Adding upstream version 0.19.0.upstream/0.19.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

35 files changed, 5662 insertions, 0 deletions

diff --git a/include/Makefile.am b/include/Makefile.am
new file mode 100644
index 0000000..242b83d
--- /dev/null
+++ b/include/Makefile.am
@@ -0,0 +1,2 @@
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diff --git a/include/Makefile.in b/include/Makefile.in
new file mode 100644
index 0000000..7797335
--- /dev/null
+++ b/include/Makefile.in
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+	info.hpp \
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+	named_expressions_iterator.hpp \
+	table.hpp \
+	types.hpp
+
+all: all-recursive
+
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+	if test -n "$$list"; then \
+	  echo " $(MKDIR_P) '$(DESTDIR)$(libixiondir)'"; \
+	  $(MKDIR_P) "$(DESTDIR)$(libixiondir)" || exit 1; \
+	fi; \
+	for p in $$list; do \
+	  if test -f "$$p"; then d=; else d="$(srcdir)/"; fi; \
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+	done | $(am__base_list) | \
+	while read files; do \
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+	  $(INSTALL_HEADER) $$files "$(DESTDIR)$(libixiondir)" || exit $$?; \
+	done
+
+uninstall-libixionHEADERS:
+	@$(NORMAL_UNINSTALL)
+	@list='$(libixion_HEADERS)'; test -n "$(libixiondir)" || list=; \
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+
+# This directory's subdirectories are mostly independent; you can cd
+# into them and run 'make' without going through this Makefile.
+# To change the values of 'make' variables: instead of editing Makefiles,
+# (1) if the variable is set in 'config.status', edit 'config.status'
+#     (which will cause the Makefiles to be regenerated when you run 'make');
+# (2) otherwise, pass the desired values on the 'make' command line.
+$(am__recursive_targets):
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+	case "$@" in \
+	  distclean-* | maintainer-clean-*) list='$(DIST_SUBDIRS)' ;; \
+	  *) list='$(SUBDIRS)' ;; \
+	esac; \
+	for subdir in $$list; do \
+	  echo "Making $$target in $$subdir"; \
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+	  if test -f "$$i"; then \
+	    echo "$(subdir)/$$i"; \
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+	    if test -d $(srcdir)/$$file && test $$d != $(srcdir); then \
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+	    cp -fpR $$d/$$file "$(distdir)$$dir" || exit 1; \
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+	    test -f "$(distdir)/$$file" \
+	    || cp -p $$d/$$file "$(distdir)/$$file" \
+	    || exit 1; \
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+	    $(am__make_dryrun) \
+	      || test -d "$(distdir)/$$subdir" \
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+	    $(am__relativize); \
+	    new_distdir=$$reldir; \
+	    dir1=$$subdir; dir2="$(top_distdir)"; \
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+check-am: all-am
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+	  test -z "$$dir" || $(MKDIR_P) "$$dir"; \
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+install-am: all-am
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+	  $(MAKE) $(AM_MAKEFLAGS) INSTALL_PROGRAM="$(INSTALL_STRIP_PROGRAM)" \
+	    install_sh_PROGRAM="$(INSTALL_STRIP_PROGRAM)" INSTALL_STRIP_FLAG=-s \
+	      install; \
+	else \
+	  $(MAKE) $(AM_MAKEFLAGS) INSTALL_PROGRAM="$(INSTALL_STRIP_PROGRAM)" \
+	    install_sh_PROGRAM="$(INSTALL_STRIP_PROGRAM)" INSTALL_STRIP_FLAG=-s \
+	    "INSTALL_PROGRAM_ENV=STRIPPROG='$(STRIP)'" install; \
+	fi
+mostlyclean-generic:
+
+clean-generic:
+
+distclean-generic:
+	-test -z "$(CONFIG_CLEAN_FILES)" || rm -f $(CONFIG_CLEAN_FILES)
+	-test . = "$(srcdir)" || test -z "$(CONFIG_CLEAN_VPATH_FILES)" || rm -f $(CONFIG_CLEAN_VPATH_FILES)
+
+maintainer-clean-generic:
+	@echo "This command is intended for maintainers to use"
+	@echo "it deletes files that may require special tools to rebuild."
+clean: clean-recursive
+
+clean-am: clean-generic clean-libtool mostlyclean-am
+
+distclean: distclean-recursive
+	-rm -f Makefile
+distclean-am: clean-am distclean-generic distclean-tags
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+dvi-am:
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+info-am:
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+	-rm -f Makefile
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+mostlyclean-am: mostlyclean-generic mostlyclean-libtool
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+.MAKE: $(am__recursive_targets) install-am install-strip
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+.PHONY: $(am__recursive_targets) CTAGS GTAGS TAGS all all-am check \
+	check-am clean clean-generic clean-libtool cscopelist-am ctags \
+	ctags-am distclean distclean-generic distclean-libtool \
+	distclean-tags distdir dvi dvi-am html html-am info info-am \
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+	mostlyclean-libtool pdf pdf-am ps ps-am tags tags-am uninstall \
+	uninstall-am uninstall-libixionHEADERS
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+.PRECIOUS: Makefile
+
+
+# Tell versions [3.59,3.63) of GNU make to not export all variables.
+# Otherwise a system limit (for SysV at least) may be exceeded.
+.NOEXPORT:
diff --git a/include/ixion/address.hpp b/include/ixion/address.hpp
new file mode 100644
index 0000000..aed09a2
--- /dev/null
+++ b/include/ixion/address.hpp
@@ -0,0 +1,347 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_ADDRESS_HPP
+#define INCLUDED_IXION_ADDRESS_HPP
+
+#include "types.hpp"
+
+#include <string>
+#include <vector>
+#include <ostream>
+#include <unordered_set>
+
+namespace ixion {
+
+/**
+ * Row address not specified. This is used to reference an entire column
+ * when a specific column address is given.
+ */
+IXION_DLLPUBLIC_VAR const row_t row_unset;
+
+/**
+ * Highest number that can be used to reference a row address. Numbers
+ * higher than this number are all used as special indices.
+ */
+IXION_DLLPUBLIC_VAR const row_t row_upper_bound;
+
+/**
+ * Column address not specified. This is used to reference an entire row
+ * when a specific row address is given.
+ */
+IXION_DLLPUBLIC_VAR const col_t column_unset;
+
+/**
+ * Highest number that can be used to reference a column address. Numbers
+ * higher than this number are all used as special indices.
+ */
+IXION_DLLPUBLIC_VAR const col_t column_upper_bound;
+
+/**
+ * Stores absolute address, and absolute address only.
+ */
+struct IXION_DLLPUBLIC abs_address_t
+{
+    enum init_invalid { invalid };
+
+    sheet_t sheet;
+    row_t   row;
+    col_t   column;
+
+    abs_address_t();
+    abs_address_t(init_invalid);
+    abs_address_t(sheet_t _sheet, row_t _row, col_t _column);
+    abs_address_t(const abs_address_t& r);
+
+    bool valid() const;
+    ::std::string get_name() const;
+
+    struct hash
+    {
+        IXION_DLLPUBLIC size_t operator() (const abs_address_t& addr) const;
+    };
+};
+
+IXION_DLLPUBLIC bool operator==(const abs_address_t& left, const abs_address_t& right);
+IXION_DLLPUBLIC bool operator!=(const abs_address_t& left, const abs_address_t& right);
+IXION_DLLPUBLIC bool operator<(const abs_address_t& left, const abs_address_t& right);
+
+/**
+ * Stores either absolute or relative address.
+ */
+struct IXION_DLLPUBLIC address_t
+{
+    sheet_t sheet;
+    row_t   row;
+    col_t   column;
+    bool    abs_sheet:1;
+    bool    abs_row:1;
+    bool    abs_column:1;
+
+    address_t();
+    address_t(sheet_t _sheet, row_t _row, col_t _column,
+              bool _abs_sheet=true, bool _abs_row=true, bool _abs_column=true);
+    address_t(const address_t& r);
+    address_t(const abs_address_t& r);
+
+    bool valid() const;
+    abs_address_t to_abs(const abs_address_t& origin) const;
+    ::std::string get_name() const;
+
+    void set_absolute(bool abs);
+
+    struct hash
+    {
+        IXION_DLLPUBLIC size_t operator() (const address_t& addr) const;
+    };
+};
+
+IXION_DLLPUBLIC bool operator==(const address_t& left, const address_t& right);
+IXION_DLLPUBLIC bool operator!=(const address_t& left, const address_t& right);
+IXION_DLLPUBLIC bool operator<(const address_t& left, const address_t& right);
+
+struct IXION_DLLPUBLIC abs_rc_address_t
+{
+    enum init_invalid { invalid };
+
+    row_t row;
+    col_t column;
+
+    abs_rc_address_t();
+    abs_rc_address_t(init_invalid);
+    abs_rc_address_t(row_t _row, col_t _column);
+    abs_rc_address_t(const abs_rc_address_t& r);
+    abs_rc_address_t(const abs_address_t& r);
+
+    bool valid() const;
+
+    struct hash
+    {
+        IXION_DLLPUBLIC size_t operator() (const abs_rc_address_t& addr) const;
+    };
+};
+
+IXION_DLLPUBLIC bool operator==(const abs_rc_address_t& left, const abs_rc_address_t& right);
+IXION_DLLPUBLIC bool operator!=(const abs_rc_address_t& left, const abs_rc_address_t& right);
+IXION_DLLPUBLIC bool operator<(const abs_rc_address_t& left, const abs_rc_address_t& right);
+
+/**
+ * Stores either absolute or relative address, but unlike the address_t
+ * counterpart, this struct only stores row and column positions.
+ */
+struct IXION_DLLPUBLIC rc_address_t
+{
+    row_t row;
+    col_t column;
+    bool  abs_row:1;
+    bool  abs_column:1;
+
+    rc_address_t();
+    rc_address_t(row_t _row, col_t _column, bool _abs_row=true, bool _abs_column=true);
+    rc_address_t(const rc_address_t& r);
+
+    struct hash
+    {
+        IXION_DLLPUBLIC size_t operator() (const rc_address_t& addr) const;
+    };
+};
+
+/**
+ * Stores absolute range address.
+ */
+struct IXION_DLLPUBLIC abs_range_t
+{
+    enum init_invalid { invalid };
+
+    abs_address_t first;
+    abs_address_t last;
+
+    abs_range_t();
+    abs_range_t(init_invalid);
+    abs_range_t(sheet_t _sheet, row_t _row, col_t _col);
+
+    /**
+     * @param _sheet 0-based sheet index.
+     * @param _row 0-based row position of the top-left cell of the range.
+     * @param _col 0-based column position of the top-left cell of the range.
+     * @param _row_span row length of the range. It must be 1 or greater.
+     * @param _col_span column length of the range.  It must be 1 or greater.
+     */
+    abs_range_t(sheet_t _sheet, row_t _row, col_t _col, row_t _row_span, col_t _col_span);
+    abs_range_t(const abs_address_t& addr);
+    abs_range_t(const abs_address_t& addr, row_t row_span, col_t col_span);
+
+    struct hash
+    {
+        IXION_DLLPUBLIC size_t operator() (const abs_range_t& range) const;
+    };
+
+    bool valid() const;
+
+    /**
+     * Expand the range horizontally to include all columns.  The row range
+     * will remain unchanged.
+     */
+    void set_all_columns();
+
+    /**
+     * Expand the range vertically to include all rows.  The column range will
+     * remain unchanged.
+     */
+    void set_all_rows();
+
+    /**
+     * @return true if the range is unspecified in the horizontal direction
+     *         i.e. all columns are selected, false otherwise.
+     */
+    bool all_columns() const;
+
+    /**
+     * @return true if the range is unspecified in the vertical direction i.e.
+     *         all rows are selected, false otherwise.
+     */
+    bool all_rows() const;
+
+    /**
+     * Check whether or not a given address is contained within this range.
+     */
+    bool contains(const abs_address_t& addr) const;
+
+    /**
+     * Reorder range values as needed to ensure the range is valid.
+     */
+    void reorder();
+};
+
+IXION_DLLPUBLIC bool operator==(const abs_range_t& left, const abs_range_t& right);
+IXION_DLLPUBLIC bool operator!=(const abs_range_t& left, const abs_range_t& right);
+IXION_DLLPUBLIC bool operator<(const abs_range_t& left, const abs_range_t& right);
+
+struct IXION_DLLPUBLIC abs_rc_range_t
+{
+    enum init_invalid { invalid };
+
+    abs_rc_address_t first;
+    abs_rc_address_t last;
+
+    abs_rc_range_t();
+    abs_rc_range_t(init_invalid);
+    abs_rc_range_t(const abs_rc_range_t& other);
+    abs_rc_range_t(const abs_range_t& other);
+
+    struct hash
+    {
+        IXION_DLLPUBLIC size_t operator() (const abs_rc_range_t& range) const;
+    };
+
+    bool valid() const;
+
+    /**
+     * Expand the range horizontally to include all columns.  The row range
+     * will remain unchanged.
+     */
+    void set_all_columns();
+
+    /**
+     * Expand the range vertically to include all rows.  The column range will
+     * remain unchanged.
+     */
+    void set_all_rows();
+
+    /**
+     * @return true if the range is unspecified in the horizontal direction
+     *         i.e. all columns are selected, false otherwise.
+     */
+    bool all_columns() const;
+
+    /**
+     * @return true if the range is unspecified in the vertical direction i.e.
+     *         all rows are selected, false otherwise.
+     */
+    bool all_rows() const;
+
+    /**
+     * Check whether or not a given address is contained within this range.
+     */
+    bool contains(const abs_rc_address_t& addr) const;
+};
+
+IXION_DLLPUBLIC bool operator==(const abs_rc_range_t& left, const abs_rc_range_t& right);
+IXION_DLLPUBLIC bool operator!=(const abs_rc_range_t& left, const abs_rc_range_t& right);
+IXION_DLLPUBLIC bool operator<(const abs_rc_range_t& left, const abs_rc_range_t& right);
+
+/**
+ * Stores range whose component may be relative or absolute.
+ */
+struct IXION_DLLPUBLIC range_t
+{
+    address_t first;
+    address_t last;
+
+    range_t();
+    range_t(const address_t& _first, const address_t& _last);
+    range_t(const range_t& r);
+    range_t(const abs_range_t& r);
+
+    bool valid() const;
+
+    /**
+     * Expand the range horizontally to include all columns.  The row range
+     * will remain unchanged.
+     */
+    void set_all_columns();
+
+    /**
+     * Expand the range vertically to include all rows.  The column range will
+     * remain unchanged.
+     */
+    void set_all_rows();
+
+    /**
+     * @return true if the range is unspecified in the horizontal direction
+     *         i.e. all columns are selected, false otherwise.
+     */
+    bool all_columns() const;
+
+    /**
+     * @return true if the range is unspecified in the vertical direction i.e.
+     *         all rows are selected, false otherwise.
+     */
+    bool all_rows() const;
+
+    abs_range_t to_abs(const abs_address_t& origin) const;
+
+    void set_absolute(bool abs);
+
+    struct hash
+    {
+        IXION_DLLPUBLIC size_t operator() (const range_t& range) const;
+    };
+};
+
+IXION_DLLPUBLIC bool operator==(const range_t& left, const range_t& right);
+IXION_DLLPUBLIC bool operator!=(const range_t& left, const range_t& right);
+
+IXION_DLLPUBLIC std::ostream& operator<<(std::ostream& os, const abs_address_t& addr);
+IXION_DLLPUBLIC std::ostream& operator<<(std::ostream& os, const abs_rc_address_t& addr);
+IXION_DLLPUBLIC std::ostream& operator<<(std::ostream& os, const address_t& addr);
+IXION_DLLPUBLIC std::ostream& operator<<(std::ostream& os, const abs_range_t& range);
+IXION_DLLPUBLIC std::ostream& operator<<(std::ostream& os, const abs_rc_range_t& range);
+IXION_DLLPUBLIC std::ostream& operator<<(std::ostream& os, const range_t& range);
+
+/**
+ * Type that represents a collection of multiple absolute cell addresses.
+ */
+using abs_address_set_t = std::unordered_set<abs_address_t, abs_address_t::hash>;
+using abs_range_set_t = std::unordered_set<abs_range_t, abs_range_t::hash>;
+using abs_rc_range_set_t = std::unordered_set<abs_rc_range_t, abs_rc_range_t::hash>;
+
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/address_iterator.hpp b/include/ixion/address_iterator.hpp
new file mode 100644
index 0000000..9250444
--- /dev/null
+++ b/include/ixion/address_iterator.hpp
@@ -0,0 +1,67 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_ADDRESS_ITERATOR_HPP
+#define INCLUDED_IXION_ADDRESS_ITERATOR_HPP
+
+#include "types.hpp"
+
+#include <memory>
+
+namespace ixion {
+
+struct abs_range_t;
+struct abs_address_t;
+
+class IXION_DLLPUBLIC abs_address_iterator
+{
+    struct impl;
+    std::unique_ptr<impl> mp_impl;
+
+public:
+    class IXION_DLLPUBLIC const_iterator
+    {
+        friend class abs_address_iterator;
+
+        struct impl_node;
+        std::unique_ptr<impl_node> mp_impl;
+
+        const_iterator(const abs_range_t& range, rc_direction_t dir, bool end);
+    public:
+        using value_type = abs_address_t;
+
+        const_iterator();
+        const_iterator(const const_iterator& r);
+        const_iterator(const_iterator&& r);
+        ~const_iterator();
+
+        const_iterator& operator++();
+        const_iterator operator++(int);
+        const_iterator& operator--();
+        const_iterator operator--(int);
+
+        const value_type& operator*() const;
+        const value_type* operator->() const;
+
+        bool operator== (const const_iterator& r) const;
+        bool operator!= (const const_iterator& r) const;
+    };
+
+    abs_address_iterator(const abs_range_t& range, rc_direction_t dir);
+    ~abs_address_iterator();
+
+    const_iterator begin() const;
+    const_iterator end() const;
+    const_iterator cbegin() const;
+    const_iterator cend() const;
+};
+
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/cell.hpp b/include/ixion/cell.hpp
new file mode 100644
index 0000000..59f09bb
--- /dev/null
+++ b/include/ixion/cell.hpp
@@ -0,0 +1,132 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_CELL_HPP
+#define INCLUDED_IXION_CELL_HPP
+
+#include "types.hpp"
+#include "formula_tokens_fwd.hpp"
+
+#include <memory>
+#include <vector>
+#include <string>
+
+namespace ixion {
+
+class formula_result;
+class formula_cell;
+class model_context;
+struct abs_address_t;
+struct rc_address_t;
+
+// calc_status is internal.
+struct calc_status;
+using calc_status_ptr_t = boost::intrusive_ptr<calc_status>;
+
+class IXION_DLLPUBLIC formula_cell
+{
+    struct impl;
+    std::unique_ptr<impl> mp_impl;
+
+public:
+    formula_cell(const formula_cell&) = delete;
+    formula_cell& operator= (formula_cell) = delete;
+
+    formula_cell();
+    formula_cell(const formula_tokens_store_ptr_t& tokens);
+
+    formula_cell(
+        row_t group_row, col_t group_col,
+        const calc_status_ptr_t& cs,
+        const formula_tokens_store_ptr_t& tokens);
+
+    ~formula_cell();
+
+    const formula_tokens_store_ptr_t& get_tokens() const;
+    void set_tokens(const formula_tokens_store_ptr_t& tokens);
+
+    double get_value(formula_result_wait_policy_t policy) const;
+    std::string_view get_string(formula_result_wait_policy_t policy) const;
+
+    void interpret(model_context& context, const abs_address_t& pos);
+
+    /**
+     * Determine if this cell contains circular reference by walking through
+     * all its reference tokens.
+     */
+    void check_circular(const model_context& cxt, const abs_address_t& pos);
+
+    /**
+     * Reset cell's internal state.
+     */
+    void reset();
+
+    /**
+     * Get a series of all reference tokens included in the formula
+     * expression stored in this cell.
+     *
+     * @param cxt model context instance.
+     * @param pos position of the cell.
+     *
+     * @return an array of reference formula tokens.  Each element is a
+     *         pointer to the actual token instance stored in the cell object.
+     *         Be aware that the pointer is valid only as long as the actual
+     *         token instance is alive.
+     */
+    std::vector<const formula_token*> get_ref_tokens(
+        const model_context& cxt, const abs_address_t& pos) const;
+
+    /**
+     * Get the cached result without post-processing in case of a grouped
+     * formula cell.
+     *
+     * @param policy action to take in case the result is not yet available.
+     *
+     * @return formula result.
+     */
+    const formula_result& get_raw_result_cache(formula_result_wait_policy_t policy) const;
+
+    /**
+     * Get the cached result as a single cell.  For a non-grouped formula
+     * cell, it should be identical to the value from the get_raw_result_cache()
+     * call.  For a grouped formula cell, you'll get a single value assigned to
+     * the position of the cell in case the original result is a matrix value.
+     *
+     * @param policy action to take in case the result is not yet available.
+     *
+     * @return formula result.
+     */
+    formula_result get_result_cache(formula_result_wait_policy_t policy) const;
+
+    /**
+     * Set a cached result to this formula cell instance.
+     *
+     *
+     * @param result cached result.
+     */
+    void set_result_cache(formula_result result);
+
+    formula_group_t get_group_properties() const;
+
+    /**
+     * Get the absolute parent position of a grouped formula cell.  If the
+     * cell is not grouped, it simply returns the original position passed to
+     * this method.
+     *
+     * @param pos original position from which to calculate the parent
+     *            position.
+     *
+     * @return parent position of the grouped formula cell.
+     */
+    abs_address_t get_parent_position(const abs_address_t& pos) const;
+};
+
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/cell_access.hpp b/include/ixion/cell_access.hpp
new file mode 100644
index 0000000..63c5323
--- /dev/null
+++ b/include/ixion/cell_access.hpp
@@ -0,0 +1,67 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_CELL_ACCESS_HPP
+#define INCLUDED_IXION_CELL_ACCESS_HPP
+
+#include "types.hpp"
+
+#include <memory>
+#include <string>
+
+namespace ixion {
+
+class model_context;
+class formula_cell;
+class formula_result;
+struct abs_address_t;
+
+/**
+ * This class provides a read-only access to a single cell.  It's more
+ * efficient to use this class if you need to make multiple successive
+ * queries to the same cell.
+ *
+ * Note that an instance of this class will get invalidated when the content
+ * of ixion::model_context is modified.
+ */
+class IXION_DLLPUBLIC cell_access
+{
+    friend class model_context;
+
+    struct impl;
+    std::unique_ptr<impl> mp_impl;
+
+    cell_access(const model_context& cxt, const abs_address_t& addr);
+public:
+    cell_access(cell_access&& other);
+    cell_access& operator= (cell_access&& other);
+    ~cell_access();
+
+    celltype_t get_type() const;
+
+    cell_value_t get_value_type() const;
+
+    const formula_cell* get_formula_cell() const;
+
+    formula_result get_formula_result() const;
+
+    double get_numeric_value() const;
+
+    bool get_boolean_value() const;
+
+    std::string_view get_string_value() const;
+
+    string_id_t get_string_identifier() const;
+
+    formula_error_t get_error_value() const;
+};
+
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/compute_engine.hpp b/include/ixion/compute_engine.hpp
new file mode 100644
index 0000000..6e5bbd7
--- /dev/null
+++ b/include/ixion/compute_engine.hpp
@@ -0,0 +1,89 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_COMPUTE_ENGINE_HPP
+#define INCLUDED_IXION_COMPUTE_ENGINE_HPP
+
+#include "env.hpp"
+#include "module.hpp"
+
+#include <memory>
+#include <string>
+
+namespace ixion { namespace draft {
+
+enum class array_type { unknown, float32, float64, uint32 };
+
+struct array
+{
+    union
+    {
+        float* float32;
+        double* float64;
+        uint32_t* uint32;
+        void* data;
+    };
+
+    array_type type = array_type::unknown;
+    std::size_t size = 0u;
+};
+
+/**
+ * Default compute engine class that uses CPU for all its computations.
+ *
+ * <p>This class also serves as the fallback for its child classes in case
+ * they don't support the function being requested or the function doesn't
+ * meet the criteria that it requires.</p>
+ *
+ * <p>Each function of this class should not modify the state of the class
+ * instance.</p>
+ */
+class IXION_DLLPUBLIC compute_engine
+{
+    struct impl;
+    std::unique_ptr<impl> mp_impl;
+
+public:
+    /**
+     * Create a compute engine instance.
+     *
+     * @param name name of the compute engine, or an empty name for the default
+     *             one.
+     *
+     * @return compute engine instance associted with the specified name. Note
+     *         that if no compute engine is registered with the specified
+     *         name, the default one is created.
+     */
+    static std::shared_ptr<compute_engine> create(std::string_view name = std::string_view());
+
+    /**
+     * Add a new compute engine class.
+     *
+     * @param hdl handler for the dynamically-loaded module in which the
+     *            compute engine being registered resides.
+     * @param name name of the compute engine.
+     * @param func_create function that creates a new instance of this compute
+     *                    engine class.
+     * @param func_destroy function that destroyes the instance of this
+     *                     compute engine class.
+     */
+    static void add_class(
+        void* hdl, std::string_view name, create_compute_engine_t func_create, destroy_compute_engine_t func_destroy);
+
+    compute_engine();
+    virtual ~compute_engine();
+
+    virtual std::string_view get_name() const;
+
+    virtual void compute_fibonacci(array& io);
+};
+
+}}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/config.hpp b/include/ixion/config.hpp
new file mode 100644
index 0000000..9575ac3
--- /dev/null
+++ b/include/ixion/config.hpp
@@ -0,0 +1,50 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_CONFIG_HPP
+#define INCLUDED_IXION_CONFIG_HPP
+
+#include "types.hpp"
+
+namespace ixion {
+
+/**
+ * This structure store parameters that influence various aspects of the
+ * ixion formula engine.
+ */
+struct IXION_DLLPUBLIC config
+{
+    /**
+     * Function argument separator.  By default it's ','.
+     */
+    char sep_function_arg;
+
+    /**
+     * Matrix column separator.
+     */
+    char sep_matrix_column;
+
+    /**
+     * Matrix row separator.
+     */
+    char sep_matrix_row;
+
+    /**
+     * Precision to use when converting a numeric value to a string
+     * representation.  A negative value indicates an unspecified precision.
+     */
+    int8_t output_precision;
+
+    config();
+    config(const config& r);
+};
+
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/dirty_cell_tracker.hpp b/include/ixion/dirty_cell_tracker.hpp
new file mode 100644
index 0000000..b701044
--- /dev/null
+++ b/include/ixion/dirty_cell_tracker.hpp
@@ -0,0 +1,97 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_DIRTY_CELL_TRACKER_HPP
+#define INCLUDED_IXION_DIRTY_CELL_TRACKER_HPP
+
+#include "address.hpp"
+
+#include <memory>
+
+namespace ixion {
+
+/**
+ * This class is designed to track in-direct dependencies of dirty formula
+ * cells.  A "dirty" formula cell is a formula cell whose result needs to be
+ * re-calculated because at least one of its references have their values
+ * updated.
+ *
+ * This class also takes volatile functions into account when determining
+ * the status of the formula cel result.  A volatile function is a cell
+ * function whose value needs to get re-calculated unconditionally on every
+ * re-calculation.  One example of a volatile function is NOW(), which
+ * returns the current time at the time of calculation.
+ */
+class IXION_DLLPUBLIC dirty_cell_tracker
+{
+    struct impl;
+    std::unique_ptr<impl> mp_impl;
+
+public:
+    dirty_cell_tracker(const dirty_cell_tracker&) = delete;
+    dirty_cell_tracker& operator= (const dirty_cell_tracker&) = delete;
+
+    dirty_cell_tracker();
+    ~dirty_cell_tracker();
+
+    /**
+     * Add a tracking relationship from a source cell or cell range to a
+     * destination cell or cell range.
+     *
+     * @param src source cell or cell range that includes reference to
+     *             (therefore listens to) the range.
+     * @param dest destination cell or range referenced tracked by the source
+     *             cell.
+     */
+    void add(const abs_range_t& src, const abs_range_t& dest);
+
+    /**
+     * Remove an existing tracking relationship from a source cell or cell
+     * range to a destination cell or cell range. If no such relationship
+     * exists, it does nothing.
+     *
+     * @param src cell or cell range that includes reference to the range.
+     * @param dest cell or range referenced by the cell.
+     */
+    void remove(const abs_range_t& src, const abs_range_t& dest);
+
+    /**
+     * Register a formula cell located at the specified position as volatile.
+     * Note that the caller should ensure that the cell at the specified
+     * position is indeed a formula cell.
+     *
+     * @param pos position of the cell to register as a volatile cell.
+     */
+    void add_volatile(const abs_range_t& pos);
+
+    /**
+     * Remove the specified cell position from the internal set of registered
+     * volatile formula cells.
+     *
+     * @param pos position of the cell to unregister as a volatile cell.
+     */
+    void remove_volatile(const abs_range_t& pos);
+
+    abs_range_set_t query_dirty_cells(const abs_range_t& modified_cell) const;
+
+    abs_range_set_t query_dirty_cells(const abs_range_set_t& modified_cells) const;
+
+    std::vector<abs_range_t> query_and_sort_dirty_cells(const abs_range_t& modified_cell) const;
+
+    std::vector<abs_range_t> query_and_sort_dirty_cells(
+        const abs_range_set_t& modified_cells, const abs_range_set_t* dirty_formula_cells = nullptr) const;
+
+    std::string to_string() const;
+
+    bool empty() const;
+};
+
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/document.hpp b/include/ixion/document.hpp
new file mode 100644
index 0000000..a612898
--- /dev/null
+++ b/include/ixion/document.hpp
@@ -0,0 +1,94 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_DOCUMENT_HPP
+#define INCLUDED_IXION_DOCUMENT_HPP
+
+#include "types.hpp"
+#include "address.hpp"
+
+#include <memory>
+#include <string>
+#include <variant>
+
+namespace ixion {
+
+class cell_access;
+
+/**
+ * Higher level document representation designed to handle both cell value
+ * storage as well as formula cell calculations.
+ */
+class IXION_DLLPUBLIC document
+{
+    struct impl;
+    std::unique_ptr<impl> mp_impl;
+public:
+    document();
+
+    /**
+     * Constructor with custom cell address type.
+     *
+     * @param cell_address_type cell address type to use for cell addresses
+     *                          represented by string values.
+     */
+    document(formula_name_resolver_t cell_address_type);
+    ~document();
+
+    struct IXION_DLLPUBLIC cell_pos
+    {
+        enum class cp_type { string, address };
+        cp_type type;
+
+        std::variant<std::string_view, ixion::abs_address_t> value;
+
+        cell_pos(const char* p);
+        cell_pos(const char* p, size_t n);
+        cell_pos(const std::string& s);
+        cell_pos(const abs_address_t& addr);
+    };
+
+    void append_sheet(std::string name);
+
+    /**
+     * Set a new name to an existing sheet.
+     *
+     * @param sheet 0-based sheet index.
+     * @param name New name of a sheet.
+     */
+    void set_sheet_name(sheet_t sheet, std::string name);
+
+    cell_access get_cell_access(cell_pos pos) const;
+
+    void set_numeric_cell(cell_pos pos, double val);
+
+    void set_string_cell(cell_pos pos, std::string_view s);
+
+    void set_boolean_cell(cell_pos pos, bool val);
+
+    void empty_cell(cell_pos pos);
+
+    double get_numeric_value(cell_pos pos) const;
+
+    std::string_view get_string_value(cell_pos pos) const;
+
+    void set_formula_cell(cell_pos pos, std::string_view formula);
+
+    /**
+     * Calculate all the "dirty" formula cells in the document.
+     *
+     * @param thread_count number of threads to use to perform calculation.
+     *                     When 0 is specified, it only uses the main thread.
+     */
+    void calculate(size_t thread_count);
+};
+
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/env.hpp b/include/ixion/env.hpp
new file mode 100644
index 0000000..c164a1d
--- /dev/null
+++ b/include/ixion/env.hpp
@@ -0,0 +1,61 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_ENV_HPP
+#define INCLUDED_IXION_ENV_HPP
+
+#if defined _WIN32 || defined __CYGWIN__
+  #if defined __MINGW32__
+    #define IXION_DLLPUBLIC
+    #define IXION_DLLPUBLIC_VAR extern
+  #elif defined IXION_BUILD
+     #ifdef DLL_EXPORT
+       #define IXION_DLLPUBLIC __declspec(dllexport)
+       #define IXION_DLLPUBLIC_VAR extern __declspec(dllexport)
+     #else
+       #define IXION_DLLPUBLIC
+       #define IXION_DLLPUBLIC_VAR extern
+     #endif
+  #else
+     #define IXION_DLLPUBLIC __declspec(dllimport)
+     #define IXION_DLLPUBLIC_VAR extern __declspec(dllimport)
+  #endif
+  #define IXION_DLLLOCAL
+#else
+  #if defined __GNUC__ && __GNUC__ >= 4
+    #define IXION_DLLPUBLIC __attribute__ ((visibility ("default")))
+    #define IXION_DLLLOCAL  __attribute__ ((visibility ("hidden")))
+  #else
+    #define IXION_DLLPUBLIC
+    #define IXION_DLLLOCAL
+  #endif
+  #define IXION_DLLPUBLIC_VAR IXION_DLLPUBLIC extern
+#endif
+
+#if _WIN32
+#define IXION_MOD_EXPORT __declspec(dllexport)
+#else
+#define IXION_MOD_EXPORT __attribute__ ((visibility ("default")))
+#endif
+
+#if defined(IXION_TRACE_ON) || defined(IXION_DEBUG_ON)
+#define IXION_LOGGING 1
+#else
+#define IXION_LOGGING 0
+#endif
+
+#ifdef __GNUC__
+  #define IXION_DEPRECATED __attribute__ ((deprecated))
+#elif defined(_MSC_VER)
+  #define IXION_DEPRECATED __declspec(deprecated)
+#else
+  #define IXION_DEPRECATED
+#endif
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/exceptions.hpp b/include/ixion/exceptions.hpp
new file mode 100644
index 0000000..bccceb1
--- /dev/null
+++ b/include/ixion/exceptions.hpp
@@ -0,0 +1,98 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_EXCEPTIONS_HPP
+#define INCLUDED_IXION_EXCEPTIONS_HPP
+
+#include "env.hpp"
+#include "types.hpp"
+
+#include <exception>
+#include <string>
+#include <memory>
+
+namespace ixion {
+
+class IXION_DLLPUBLIC general_error : public std::exception
+{
+public:
+    general_error();
+    explicit general_error(const std::string& msg);
+    virtual ~general_error();
+    virtual const char* what() const noexcept override;
+
+protected:
+    void set_message(const std::string& msg);
+
+private:
+    std::string m_msg;
+};
+
+class IXION_DLLPUBLIC formula_error : public std::exception
+{
+    struct impl;
+    std::unique_ptr<impl> mp_impl;
+public:
+    explicit formula_error(formula_error_t fe);
+    explicit formula_error(formula_error_t fe, std::string msg);
+    formula_error(formula_error&& other);
+
+    virtual ~formula_error();
+    virtual const char* what() const noexcept override;
+
+    formula_error_t get_error() const;
+};
+
+class IXION_DLLPUBLIC file_not_found : public general_error
+{
+public:
+    explicit file_not_found(const std::string& fpath);
+    virtual ~file_not_found() override;
+};
+
+class IXION_DLLPUBLIC formula_registration_error : public general_error
+{
+public:
+    explicit formula_registration_error(const std::string& msg);
+    virtual ~formula_registration_error() override;
+};
+
+/**
+ * This exception is thrown typically from the ixion::model_context class.
+ */
+class IXION_DLLPUBLIC model_context_error: public general_error
+{
+public:
+    enum error_type
+    {
+        circular_dependency,
+        invalid_named_expression,
+        sheet_name_conflict,
+        sheet_size_locked,
+        not_implemented
+    };
+
+    explicit model_context_error(const std::string& msg, error_type type);
+    virtual ~model_context_error() override;
+
+    error_type get_error_type() const;
+
+private:
+    error_type m_type;
+};
+
+class IXION_DLLPUBLIC not_implemented_error : public general_error
+{
+public:
+    explicit not_implemented_error(const std::string& msg);
+    virtual ~not_implemented_error() override;
+};
+
+}
+
+#endif
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/formula.hpp b/include/ixion/formula.hpp
new file mode 100644
index 0000000..f15c72d
--- /dev/null
+++ b/include/ixion/formula.hpp
@@ -0,0 +1,217 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_FORMULA_HPP
+#define INCLUDED_IXION_FORMULA_HPP
+
+#include "formula_tokens.hpp"
+#include "types.hpp"
+#include "env.hpp"
+
+#include <string>
+
+namespace ixion {
+
+class formula_cell;
+class formula_name_resolver;
+class model_context;
+
+/**
+ * Parse a raw formula expression string into formula tokens.
+ *
+ * @param cxt model context.
+ * @param pos address of the cell that has the formula expression.
+ * @param resolver name resolver object used to resolve name tokens.
+ * @param formula raw formula expression string to parse.
+ *
+ * @return formula tokens representing the parsed formula expression.
+ */
+IXION_DLLPUBLIC formula_tokens_t parse_formula_string(
+    model_context& cxt, const abs_address_t& pos,
+    const formula_name_resolver& resolver, std::string_view formula);
+
+/**
+ * Create a set of tokens that represent an invalid formula.
+ *
+ * This can be used for a cell containing an invalid formula expression, and
+ * the error information needs to be preserved.
+ *
+ * @param cxt model context.
+ * @param src_formula original formula string.
+ * @param error error string.
+ *
+ * @return a set of tokens, the first of which is a token of type fop_error,
+ *         followed by two string tokens.  The second token stores the
+ *         original formula string, whereas the third one stores the error
+ *         string.  The first token stores the number of tokens that follows
+ *         as its value of type std::size_t, which is always 2 in the current
+ *         implementation.
+ */
+IXION_DLLPUBLIC formula_tokens_t create_formula_error_tokens(
+    model_context& cxt, std::string_view src_formula,
+    std::string_view error);
+
+/**
+ * Convert formula tokens into a human-readable string representation.
+ *
+ * @param cxt model context.
+ * @param pos address of the cell that has the formula tokens.
+ * @param resolver name resolver object used to print name tokens.
+ * @param tokens formula tokens.
+ *
+ * @return string representation of the formula tokens.
+ */
+IXION_DLLPUBLIC std::string print_formula_tokens(
+    const model_context& cxt, const abs_address_t& pos,
+    const formula_name_resolver& resolver, const formula_tokens_t& tokens);
+
+/**
+ * Convert formula tokens into a human-readable string representation.
+ *
+ * @param config Configuration options for printing preferences.
+ * @param cxt Model context.
+ * @param pos Address of the cell that has the formula tokens.
+ * @param resolver Name resolver object used to print name tokens.
+ * @param tokens Formula tokens to print.
+ *
+ * @return string representation of the formula tokens.
+ */
+IXION_DLLPUBLIC std::string print_formula_tokens(
+    const print_config& config, const model_context& cxt, const abs_address_t& pos,
+    const formula_name_resolver& resolver, const formula_tokens_t& tokens);
+
+/**
+ * Convert an individual formula token into a human-readable string
+ * representation.
+ *
+ * @param cxt model context.
+ * @param pos address of the cell that has the formula tokens.
+ * @param resolver name resolver object used to print name tokens.
+ * @param token formula token to convert.
+ *
+ * @return string representation of the formula token.
+ */
+IXION_DLLPUBLIC std::string print_formula_token(
+    const model_context& cxt, const abs_address_t& pos,
+    const formula_name_resolver& resolver, const formula_token& token);
+
+/**
+ * Convert an individual formula token into a human-readable string
+ * representation.
+ *
+ * @param config Configuration options for printing preferences.
+ * @param cxt Model context.
+ * @param pos Address of the cell that has the formula tokens.
+ * @param resolver Name resolver object used to print name tokens.
+ * @param token Formula token to convert.
+ *
+ * @return string representation of the formula token.
+ */
+IXION_DLLPUBLIC std::string print_formula_token(
+    const print_config& config, const model_context& cxt, const abs_address_t& pos,
+    const formula_name_resolver& resolver, const formula_token& token);
+
+/**
+ * Regisiter a formula cell with cell dependency tracker.
+ *
+ * @param cxt model context.
+ * @param pos address of the cell being registered.  In case of grouped
+ *            cells, the position must be that of teh top-left cell of that
+ *            group.
+ * @param cell (optional) pointer to the formula cell object to register.
+ *             You can skip this parameter, in which case the formula cell
+ *             object will be fetched from the address of the cell.  But
+ *             passing a pointer will save the overhead of fetching.
+ */
+void IXION_DLLPUBLIC register_formula_cell(
+    model_context& cxt, const abs_address_t& pos, const formula_cell* cell = nullptr);
+
+/**
+ * Unregister a formula cell with cell dependency tracker if a formula cell
+ * exists at specified cell address.  If there is no existing cell at the
+ * specified address, or the cell is not a formula cell, this function is a
+ * no-op.
+ *
+ * @param cxt model context.
+ * @param pos address of the cell being unregistered.
+ */
+void IXION_DLLPUBLIC unregister_formula_cell(
+    model_context& cxt, const abs_address_t& pos);
+
+/**
+ * Get the positions of those formula cells that directly or indirectly
+ * depend on the specified source cells.
+ *
+ * @param cxt model context.
+ * @param modified_cells collection of the postiions of cells that have been
+ *                       modified.
+ *
+ * @return collection of the positions of formula cells that directly or
+ *         indirectly depend on at least one of the specified source cells.
+ */
+IXION_DLLPUBLIC abs_address_set_t query_dirty_cells(
+    model_context& cxt, const abs_address_set_t& modified_cells);
+
+/**
+ * Get a sequence of the positions of all formula cells that track at least
+ * one of the specified modified cells either directly or indirectly.  Such
+ * formula cells are referred to as "dirty" formula cells.  The sequence
+ * returned from this function is already sorted in topological order based
+ * on the dependency relationships between the affected formula cells.  Note
+ * that if the model contains volatile formula cells, they will be included
+ * in the returned sequence each and every time.
+ *
+ * Use query_dirty_cells() instead if you don't need the results to be sorted
+ * in order of dependency, to avoid the extra overhead incurred by the
+ * sorting.
+ *
+ * @param cxt model context.
+ * @param modified_cells a collection of non-formula cells whose values have
+ *                       been updated.  You can specify one or more ranges
+ *                       of cells rather than individual cell positions.
+ * @param dirty_formula_cells (optional) a collection of formula cells that
+ *                            are already known to be dirty.  These formula
+ *                            cells will be added to the list of the
+ *                            affected formula cells returned from this
+ *                            function.  Note that even though this
+ *                            parameter is a set of cell ranges, regular
+ *                            formula cell positions must be given as single
+ *                            cell addresses.  Only the positions of grouped
+ *                            formula cells must be given as ranges.
+ *
+ * @return an sequence containing the positions of the formula cells that
+ *         track at least one of the modified cells, as well as those
+ *         formula cells that are already known to be dirty.
+ */
+IXION_DLLPUBLIC std::vector<abs_range_t> query_and_sort_dirty_cells(
+    model_context& cxt, const abs_range_set_t& modified_cells,
+    const abs_range_set_t* dirty_formula_cells = nullptr);
+
+/**
+ * Calculate all specified formula cells in the order they occur in the
+ * sequence.
+ *
+ * @param cxt model context.
+ * @param formula_cells formula cells to be calculated.  The cells will be
+ *                      calculated in the order they appear in the sequence.
+ *                      In a typical use case, this will be the returned
+ *                      value from query_and_sort_dirty_cells.
+ * @param thread_count number of calculation threads to use.  Note that
+ *                     passing 0 will make the process use the main thread
+ *                     only, while passing any number greater than 0 will
+ *                     make the process spawn specified number of
+ *                     calculation threads plus one additional thread to
+ *                     manage the calculation threads.
+ */
+void IXION_DLLPUBLIC calculate_sorted_cells(
+    model_context& cxt, const std::vector<abs_range_t>& formula_cells, size_t thread_count);
+
+} // namespace ixion
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/formula_function_opcode.hpp b/include/ixion/formula_function_opcode.hpp
new file mode 100644
index 0000000..ddfabc3
--- /dev/null
+++ b/include/ixion/formula_function_opcode.hpp
@@ -0,0 +1,370 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_FORMULA_FUNCTION_OPCODE_HPP
+#define INCLUDED_IXION_FORMULA_FUNCTION_OPCODE_HPP
+
+#include "env.hpp"
+
+#include <cstdint>
+#include <string_view>
+
+namespace ixion {
+
+/**
+ * Enum that represents built-in formula functions.
+ */
+enum class formula_function_t : uint16_t
+{
+    func_unknown = 0,
+    func_abs,
+    func_acos,
+    func_acosh,
+    func_acot,
+    func_acoth,
+    func_address,
+    func_aggregate,
+    func_and,
+    func_arabic,
+    func_areas,
+    func_asc,
+    func_asin,
+    func_asinh,
+    func_atan,
+    func_atan2,
+    func_atanh,
+    func_avedev,
+    func_average,
+    func_averagea,
+    func_averageif,
+    func_averageifs,
+    func_b,
+    func_bahttext,
+    func_base,
+    func_betadist,
+    func_betainv,
+    func_binomdist,
+    func_bitand,
+    func_bitlshift,
+    func_bitor,
+    func_bitrshift,
+    func_bitxor,
+    func_ceiling,
+    func_cell,
+    func_char,
+    func_chidist,
+    func_chiinv,
+    func_chisqdist,
+    func_chisqinv,
+    func_chitest,
+    func_choose,
+    func_clean,
+    func_code,
+    func_color,
+    func_column,
+    func_columns,
+    func_combin,
+    func_combina,
+    func_concat,
+    func_concatenate,
+    func_confidence,
+    func_correl,
+    func_cos,
+    func_cosh,
+    func_cot,
+    func_coth,
+    func_count,
+    func_counta,
+    func_countblank,
+    func_countif,
+    func_countifs,
+    func_covar,
+    func_critbinom,
+    func_csc,
+    func_csch,
+    func_cumipmt,
+    func_cumprinc,
+    func_current,
+    func_date,
+    func_datedif,
+    func_datevalue,
+    func_daverage,
+    func_day,
+    func_days,
+    func_days360,
+    func_db,
+    func_dcount,
+    func_dcounta,
+    func_ddb,
+    func_dde,
+    func_decimal,
+    func_degrees,
+    func_devsq,
+    func_dget,
+    func_dmax,
+    func_dmin,
+    func_dollar,
+    func_dproduct,
+    func_dstdev,
+    func_dstdevp,
+    func_dsum,
+    func_dvar,
+    func_dvarp,
+    func_eastersunday,
+    func_effect,
+    func_encodeurl,
+    func_errortype,
+    func_euroconvert,
+    func_even,
+    func_exact,
+    func_exp,
+    func_expondist,
+    func_fact,
+    func_false,
+    func_fdist,
+    func_filterxml,
+    func_find,
+    func_findb,
+    func_finv,
+    func_fisher,
+    func_fisherinv,
+    func_fixed,
+    func_floor,
+    func_forecast,
+    func_formula,
+    func_fourier,
+    func_frequency,
+    func_ftest,
+    func_fv,
+    func_gamma,
+    func_gammadist,
+    func_gammainv,
+    func_gammaln,
+    func_gauss,
+    func_gcd,
+    func_geomean,
+    func_getpivotdata,
+    func_goalseek,
+    func_growth,
+    func_harmean,
+    func_hlookup,
+    func_hour,
+    func_hyperlink,
+    func_hypgeomdist,
+    func_if,
+    func_iferror,
+    func_ifna,
+    func_ifs,
+    func_index,
+    func_indirect,
+    func_info,
+    func_int,
+    func_intercept,
+    func_ipmt,
+    func_irr,
+    func_isblank,
+    func_iserr,
+    func_iserror,
+    func_iseven,
+    func_isformula,
+    func_islogical,
+    func_isna,
+    func_isnontext,
+    func_isnumber,
+    func_isodd,
+    func_isoweeknum,
+    func_ispmt,
+    func_isref,
+    func_istext,
+    func_jis,
+    func_kurt,
+    func_large,
+    func_lcm,
+    func_left,
+    func_leftb,
+    func_len,
+    func_lenb,
+    func_linest,
+    func_ln,
+    func_log,
+    func_log10,
+    func_logest,
+    func_loginv,
+    func_lognormdist,
+    func_lookup,
+    func_lower,
+    func_match,
+    func_max,
+    func_maxa,
+    func_maxifs,
+    func_mdeterm,
+    func_median,
+    func_mid,
+    func_midb,
+    func_min,
+    func_mina,
+    func_minifs,
+    func_minute,
+    func_minverse,
+    func_mirr,
+    func_mmult,
+    func_mod,
+    func_mode,
+    func_month,
+    func_multirange,
+    func_munit,
+    func_mvalue,
+    func_n,
+    func_na,
+    func_neg,
+    func_negbinomdist,
+    func_networkdays,
+    func_nominal,
+    func_normdist,
+    func_norminv,
+    func_normsdist,
+    func_normsinv,
+    func_not,
+    func_now,
+    func_nper,
+    func_npv,
+    func_numbervalue,
+    func_odd,
+    func_offset,
+    func_or,
+    func_pduration,
+    func_pearson,
+    func_percentile,
+    func_percentrank,
+    func_permut,
+    func_permutationa,
+    func_phi,
+    func_pi,
+    func_pmt,
+    func_poisson,
+    func_power,
+    func_ppmt,
+    func_prob,
+    func_product,
+    func_proper,
+    func_pv,
+    func_quartile,
+    func_radians,
+    func_rand,
+    func_rank,
+    func_rate,
+    func_rawsubtract,
+    func_regex,
+    func_replace,
+    func_replaceb,
+    func_rept,
+    func_right,
+    func_rightb,
+    func_roman,
+    func_round,
+    func_rounddown,
+    func_roundsig,
+    func_roundup,
+    func_row,
+    func_rows,
+    func_rri,
+    func_rsq,
+    func_search,
+    func_searchb,
+    func_sec,
+    func_sech,
+    func_second,
+    func_sheet,
+    func_sheets,
+    func_sign,
+    func_sin,
+    func_sinh,
+    func_skew,
+    func_skewp,
+    func_sln,
+    func_slope,
+    func_small,
+    func_sqrt,
+    func_standardize,
+    func_stdev,
+    func_stdeva,
+    func_stdevp,
+    func_stdevpa,
+    func_steyx,
+    func_style,
+    func_substitute,
+    func_subtotal,
+    func_sum,
+    func_sumif,
+    func_sumifs,
+    func_sumproduct,
+    func_sumsq,
+    func_sumx2my2,
+    func_sumx2py2,
+    func_sumxmy2,
+    func_switch,
+    func_syd,
+    func_t,
+    func_tan,
+    func_tanh,
+    func_tdist,
+    func_text,
+    func_textjoin,
+    func_time,
+    func_timevalue,
+    func_tinv,
+    func_today,
+    func_transpose,
+    func_trend,
+    func_trim,
+    func_trimmean,
+    func_true,
+    func_trunc,
+    func_ttest,
+    func_type,
+    func_unichar,
+    func_unicode,
+    func_upper,
+    func_value,
+    func_var,
+    func_vara,
+    func_varp,
+    func_varpa,
+    func_vdb,
+    func_vlookup,
+    func_wait,
+    func_webservice,
+    func_weekday,
+    func_weeknum,
+    func_weibull,
+    func_xor,
+    func_year,
+    func_ztest,
+};
+
+/**
+ * Get a string representation of a formula function opcode.
+ *
+ * @param func formula function opcode.
+ *
+ * @return string representation of the opcode.
+ */
+IXION_DLLPUBLIC std::string_view get_formula_function_name(formula_function_t func);
+
+/**
+ * Get a formula function opcode from a formula function name.
+ *
+ * @param s formula function name.
+ *
+ * @return formula function opcode representing the specified name.
+ */
+IXION_DLLPUBLIC formula_function_t get_formula_function_opcode(std::string_view s);
+
+}
+
+#endif
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/formula_name_resolver.hpp b/include/ixion/formula_name_resolver.hpp
new file mode 100644
index 0000000..eb2a8a9
--- /dev/null
+++ b/include/ixion/formula_name_resolver.hpp
@@ -0,0 +1,129 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_FORMULA_NAME_RESOLVER_HPP
+#define INCLUDED_IXION_FORMULA_NAME_RESOLVER_HPP
+
+#include "address.hpp"
+#include "formula_function_opcode.hpp"
+
+#include <string>
+#include <memory>
+#include <variant>
+
+namespace ixion {
+
+class model_context;
+struct table_t;
+
+/**
+ * Structure that represents the type of a 'name' in a formula expression.
+ *
+ * A name can be either one of:
+ * <ul>
+ * <li>cell reference</li>
+ * <li>range reference</li>
+ * <li>table reference</li>
+ * <li>named expression</li>
+ * <li>function</li>
+ * </ul>
+ */
+struct IXION_DLLPUBLIC formula_name_t
+{
+    enum name_type
+    {
+        invalid = 0,
+        cell_reference,
+        range_reference,
+        table_reference,
+        named_expression,
+        function
+    };
+
+    /**
+     * Table information for a table reference name.  Unlike the ixion::table_t
+     * counterpart, we store strings as string views as the resolver doesn't
+     * have access to the string pool.
+     */
+    struct table_type
+    {
+        std::string_view name;
+        std::string_view column_first;
+        std::string_view column_last;
+        table_areas_t areas;
+    };
+
+    using value_type = std::variant<address_t, range_t, table_type, formula_function_t>;
+
+    name_type type;
+    value_type value;
+
+    formula_name_t();
+
+    /**
+     * Return a string that represents the data stored internally.  Useful for
+     * debugging.
+     */
+    std::string to_string() const;
+};
+
+/**
+ * Formula name resolvers resolves a name in a formula expression to a more
+ * concrete name type.
+ */
+class formula_name_resolver
+{
+public:
+    formula_name_resolver();
+    virtual ~formula_name_resolver() = 0;
+
+    /**
+     * Parse and resolve a reference string.
+     *
+     * @param s reference string to be parsed.
+     * @param pos base cell position, which influences the resolved reference
+     *            position(s) containing relative address(es).  When the
+     *            reference string does not contain an explicit sheet name,
+     *            the sheet address of the base cell position is used.
+     *
+     * @return result of the resovled reference.
+     */
+    virtual formula_name_t resolve(std::string_view s, const abs_address_t& pos) const = 0;
+    virtual std::string get_name(const address_t& addr, const abs_address_t& pos, bool sheet_name) const = 0;
+    virtual std::string get_name(const range_t& range, const abs_address_t& pos, bool sheet_name) const = 0;
+    virtual std::string get_name(const table_t& table) const = 0;
+
+    /**
+     * Given a numerical representation of column position, return its
+     * textural representation.
+     *
+     * @param col numerical column position.
+     *
+     * @return textural representation of column position.
+     */
+    virtual std::string get_column_name(col_t col) const = 0;
+
+    /**
+     * Create a formula name resolver instance according to the requested
+     * type.
+     *
+     * @param type type formula name resolver being requested.
+     * @param cxt document model context for resolving sheet names, or nullptr
+     *            in case names being resolved don't contain sheet names.
+     *
+     * @return formula name resolver instance created on the heap.  The caller
+     *         is responsible for managing its life cycle.
+     */
+    IXION_DLLPUBLIC static std::unique_ptr<formula_name_resolver>
+        get(formula_name_resolver_t type, const model_context* cxt);
+};
+
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/formula_opcode.hpp b/include/ixion/formula_opcode.hpp
new file mode 100644
index 0000000..1f3d71b
--- /dev/null
+++ b/include/ixion/formula_opcode.hpp
@@ -0,0 +1,61 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_FORMULA_OPCODE_HPP
+#define INCLUDED_IXION_FORMULA_OPCODE_HPP
+
+namespace ixion {
+
+/** formula opcode type */
+enum fopcode_t
+{
+    fop_unknown = 0,
+
+    // data types
+    fop_single_ref,
+    fop_range_ref,
+    fop_table_ref,
+    fop_named_expression,
+    fop_string,
+    fop_value,
+    fop_function,
+
+    // arithmetic operators
+    fop_plus,
+    fop_minus,
+    fop_divide,
+    fop_multiply,
+    fop_exponent,
+
+    // string operators
+    fop_concat,
+
+    // relational operators
+    fop_equal,
+    fop_not_equal,
+    fop_less,
+    fop_greater,
+    fop_less_equal,
+    fop_greater_equal,
+
+    // parentheses, separators
+    fop_open,
+    fop_close,
+    fop_sep,
+    fop_array_row_sep,
+    fop_array_open,
+    fop_array_close,
+
+    // special conditions
+    fop_error, //< used to signify a special set of tokens representing formula cell with error.
+};
+
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/formula_result.hpp b/include/ixion/formula_result.hpp
new file mode 100644
index 0000000..551af18
--- /dev/null
+++ b/include/ixion/formula_result.hpp
@@ -0,0 +1,136 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_FORMULA_RESULT_HPP
+#define INCLUDED_IXION_FORMULA_RESULT_HPP
+
+#include "global.hpp"
+
+#include <string>
+#include <memory>
+#include <iosfwd>
+
+namespace ixion {
+
+class matrix;
+class model_context;
+
+/**
+ * Store formula result which may be either numeric, textural, or error.  In
+ * case the result is textural, it owns the instance of the string.
+ */
+class IXION_DLLPUBLIC formula_result
+{
+    struct impl;
+    std::unique_ptr<impl> mp_impl;
+
+public:
+    enum class result_type { boolean, value, string, error, matrix };
+
+    formula_result();
+    formula_result(const formula_result& r);
+    formula_result(formula_result&& r);
+    formula_result(bool b);
+    formula_result(double v);
+    formula_result(std::string str);
+    formula_result(formula_error_t e);
+    formula_result(matrix mtx);
+    ~formula_result();
+
+    void reset();
+    void set_boolean(bool b);
+    void set_value(double v);
+    void set_string_value(std::string str);
+    void set_error(formula_error_t e);
+    void set_matrix(matrix mtx);
+
+    /**
+     * Get a boolean result value.  The caller must make sure the result is of
+     * boolean type, else the behavior is undefined.
+     *
+     * @return boolean result value.
+     */
+    bool get_boolean() const;
+
+    /**
+     * Get a numeric result value.  The caller must make sure the result is of
+     * numeric type, else the behavior is undefined.
+     *
+     * @return numeric result value.
+     */
+    double get_value() const;
+
+    /**
+     * Get a string value for textural result.  The caller must make
+     * sure the result is of textural type, else the behavior is undefined.
+     *
+     * @return string value.
+     */
+    const std::string& get_string() const;
+
+    /**
+     * Get an error value of the result.  The caller must make sure that the
+     * result is of error type, else the behavior is undefined.
+     *
+     * @return enum value representing the error.
+     * @see ixion::get_formula_error_name
+     */
+    formula_error_t get_error() const;
+
+    /**
+     * Get a matrix value of the result.  The caller must make sure that the
+     * result is of matrix type, else the behavior is undefined.
+     *
+     * @return matrix result value.
+     */
+    const matrix& get_matrix() const;
+
+    /**
+     * Get a matrix value of the result.  The caller must make sure that the
+     * result is of matrix type, else the behavior is undefined.
+     *
+     * @return matrix result value.
+     */
+    matrix& get_matrix();
+
+    /**
+     * Get the type of result.
+     *
+     * @return enum value representing the result type.
+     */
+    result_type get_type() const;
+
+    /**
+     * Get a string representation of the result value no matter what the
+     * result type is.
+     *
+     * @param cxt model context object.
+     *
+     * @return string representation of the result value.
+     */
+    std::string str(const model_context& cxt) const;
+
+    /**
+     * Parse a textural representation of a formula result, and set result
+     * value of appropriate type.
+     *
+     * @param s formula result as a string.
+     */
+    void parse(std::string_view s);
+
+    formula_result& operator= (formula_result r);
+    bool operator== (const formula_result& r) const;
+    bool operator!= (const formula_result& r) const;
+};
+
+IXION_DLLPUBLIC std::ostream& operator<< (std::ostream& os, formula_result::result_type v);
+
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/formula_tokens.hpp b/include/ixion/formula_tokens.hpp
new file mode 100644
index 0000000..d843dbd
--- /dev/null
+++ b/include/ixion/formula_tokens.hpp
@@ -0,0 +1,215 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_FORMULA_TOKENS_HPP
+#define INCLUDED_FORMULA_TOKENS_HPP
+
+#include "address.hpp"
+#include "table.hpp"
+#include "formula_opcode.hpp"
+#include "formula_function_opcode.hpp"
+#include "formula_tokens_fwd.hpp"
+
+#include <string>
+#include <variant>
+
+namespace ixion {
+
+/**
+ * Get a printable name for a formula opcode.  The printable name is to be
+ * used only for informational purposes.
+ *
+ * @param oc formula opcode
+ *
+ * @return printable name for a formula opcode.
+ */
+IXION_DLLPUBLIC std::string_view get_opcode_name(fopcode_t oc);
+
+/**
+ * Get the string representation of a simple formula opcode.  This function
+ * will return a non-empty string only for operator opcodes.
+ *
+ * @param oc formula opcode
+ *
+ * @return string representation of a formula opcode.
+ */
+IXION_DLLPUBLIC std::string_view get_formula_opcode_string(fopcode_t oc);
+
+/**
+ * Represents a single formula token.
+ */
+struct IXION_DLLPUBLIC formula_token final
+{
+    using value_type = std::variant<
+        address_t, range_t, table_t, formula_function_t,
+        double, string_id_t, std::string>;
+
+    /**
+     * Opcode that specifies the type of token.  The value of this data member
+     * should <i>not</i> be modified after construction.
+     */
+    const fopcode_t opcode;
+
+    /**
+     * Value stored in the token. The type of this value varies depending on the
+     * token opcode value.
+     */
+    value_type value;
+
+    formula_token() = delete;
+
+    /**
+     * Constructor for opcode-only token.
+     *
+     * @param op formula opcode.
+     */
+    formula_token(fopcode_t op);
+
+    /**
+     * Constructor for a single-cell reference token.  The opcode will be
+     * implicitly set to fop_single_ref.
+     *
+     * @param addr single-cell reference.
+     */
+    formula_token(const address_t& addr);
+
+    /**
+     * Constructor for a range reference token.  The opcode will be
+     * implicitly set to fop_range_ref.
+     *
+     * @param range range reference.
+     */
+    formula_token(const range_t& range);
+
+    /**
+     * Constructor for a table reference token.  The opcode will be implicitly
+     * set to fop_table_ref.
+     *
+     * @param table table reference.
+     */
+    formula_token(const table_t& table);
+
+    /**
+     * Constructor for a formula function token.  The opcode will be implicitly
+     * set to fop_function.
+     *
+     * @param func function name enum value.
+     */
+    formula_token(formula_function_t func);
+
+    /**
+     * Constructor for a numeric value token.  The opcode will be implicitly set
+     * to fop_value.
+     *
+     * @param v numeric value to be stored in the token.
+     */
+    formula_token(double v);
+
+    /**
+     * Constructor for a string value token.  The opcode will be implicitly
+     * set to fop_string.
+     *
+     * @param sid string ID to be stored in the token.
+     */
+    formula_token(string_id_t sid);
+
+    /**
+     * Constructor for a named-expression token.  The opcode will be implicitly
+     * set to fop_named_expression.
+     *
+     * @param name named expression to be stored in the token.
+     */
+    formula_token(std::string name);
+
+    /**
+     * Copy constructor.
+     */
+    formula_token(const formula_token& r);
+
+    /**
+     * Move constructor.
+     *
+     * @note This will be the same as the copy constructor if the stored value
+     *       is not movable.
+     */
+    formula_token(formula_token&& r);
+
+    ~formula_token();
+
+    bool operator== (const formula_token& r) const;
+    bool operator!= (const formula_token& r) const;
+};
+
+/**
+ * Storage for a series of formula tokens.
+ */
+class IXION_DLLPUBLIC formula_tokens_store
+{
+    friend void intrusive_ptr_add_ref(formula_tokens_store*);
+    friend void intrusive_ptr_release(formula_tokens_store*);
+
+    struct impl;
+    std::unique_ptr<impl> mp_impl;
+
+    void add_ref();
+    void release_ref();
+
+    formula_tokens_store();
+
+public:
+
+    static formula_tokens_store_ptr_t create();
+
+    ~formula_tokens_store();
+
+    formula_tokens_store(const formula_tokens_store&) = delete;
+    formula_tokens_store& operator= (const formula_tokens_store&) = delete;
+
+    size_t get_reference_count() const;
+
+    formula_tokens_t& get();
+    const formula_tokens_t& get() const;
+};
+
+inline void intrusive_ptr_add_ref(formula_tokens_store* p)
+{
+    p->add_ref();
+}
+
+inline void intrusive_ptr_release(formula_tokens_store* p)
+{
+    p->release_ref();
+}
+
+/**
+ * Represents a named expression which stores a series of formula tokens.
+ */
+struct IXION_DLLPUBLIC named_expression_t
+{
+    /**
+     * Origin cell position which affects any relative references stored in
+     * the named expression.
+     */
+    abs_address_t origin;
+
+    /** Formula tokens. */
+    formula_tokens_t tokens;
+
+    named_expression_t();
+    named_expression_t(const abs_address_t& _origin, formula_tokens_t _tokens);
+    named_expression_t(const named_expression_t&) = delete;
+    named_expression_t(named_expression_t&& other);
+    ~named_expression_t();
+};
+
+IXION_DLLPUBLIC std::ostream& operator<< (std::ostream& os, const formula_token& ft);
+
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/formula_tokens_fwd.hpp b/include/ixion/formula_tokens_fwd.hpp
new file mode 100644
index 0000000..4e8dd50
--- /dev/null
+++ b/include/ixion/formula_tokens_fwd.hpp
@@ -0,0 +1,27 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_FORMULA_TOKENS_FWD_HPP
+#define INCLUDED_IXION_FORMULA_TOKENS_FWD_HPP
+
+#include <boost/intrusive_ptr.hpp>
+#include <vector>
+#include <memory>
+
+namespace ixion {
+
+struct formula_token;
+class formula_tokens_store;
+using formula_tokens_store_ptr_t = boost::intrusive_ptr<formula_tokens_store>;
+using formula_tokens_t = std::vector<formula_token>;
+struct named_expression_t;
+
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/global.hpp b/include/ixion/global.hpp
new file mode 100644
index 0000000..4f8aa46
--- /dev/null
+++ b/include/ixion/global.hpp
@@ -0,0 +1,35 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_GLOBAL_HPP
+#define INCLUDED_IXION_GLOBAL_HPP
+
+#include "types.hpp"
+#include "env.hpp"
+
+#include <memory>
+#include <string>
+
+namespace ixion {
+
+/**
+ * Get current time in seconds since epoch.  Note that the value
+ * representing a time may differ from platform to platform.  Use this
+ * value only to measure relative time.
+ *
+ * @return current time in seconds since epoch.
+ */
+IXION_DLLPUBLIC double get_current_time();
+
+IXION_DLLPUBLIC double to_double(std::string_view s);
+
+IXION_DLLPUBLIC bool to_bool(std::string_view s);
+
+}
+
+#endif
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/info.hpp b/include/ixion/info.hpp
new file mode 100644
index 0000000..1d7a41f
--- /dev/null
+++ b/include/ixion/info.hpp
@@ -0,0 +1,26 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_INFO_HPP
+#define INCLUDED_IXION_INFO_HPP
+
+#include "env.hpp"
+
+namespace ixion {
+
+IXION_DLLPUBLIC int get_version_major();
+IXION_DLLPUBLIC int get_version_minor();
+IXION_DLLPUBLIC int get_version_micro();
+
+IXION_DLLPUBLIC int get_api_version_major();
+IXION_DLLPUBLIC int get_api_version_minor();
+
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/interface/Makefile.am b/include/ixion/interface/Makefile.am
new file mode 100644
index 0000000..8b3fdc3
--- /dev/null
+++ b/include/ixion/interface/Makefile.am
@@ -0,0 +1,6 @@
+
+libixiondir = $(includedir)/libixion-@IXION_API_VERSION@/ixion/interface
+
+libixion_HEADERS = \
+	session_handler.hpp \
+	table_handler.hpp
diff --git a/include/ixion/interface/Makefile.in b/include/ixion/interface/Makefile.in
new file mode 100644
index 0000000..f17c341
--- /dev/null
+++ b/include/ixion/interface/Makefile.in
@@ -0,0 +1,611 @@
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diff --git a/include/ixion/interface/session_handler.hpp b/include/ixion/interface/session_handler.hpp
new file mode 100644
index 0000000..7ed2a8e
--- /dev/null
+++ b/include/ixion/interface/session_handler.hpp
@@ -0,0 +1,50 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef __IXION_INTERFACE_SESSION_HANDLER_HPP__
+#define __IXION_INTERFACE_SESSION_HANDLER_HPP__
+
+#include "../formula_opcode.hpp"
+#include "../formula_function_opcode.hpp"
+#include "../env.hpp"
+
+#include <cstdlib>
+
+namespace ixion {
+
+class formula_cell;
+class formula_result;
+struct address_t;
+struct range_t;
+struct abs_address_t;
+struct table_t;
+
+namespace iface {
+
+class IXION_DLLPUBLIC session_handler
+{
+public:
+    virtual ~session_handler();
+
+    virtual void begin_cell_interpret(const abs_address_t& pos) = 0;
+    virtual void end_cell_interpret() = 0;
+    virtual void set_result(const formula_result& result) = 0;
+    virtual void set_invalid_expression(std::string_view msg) = 0;
+    virtual void set_formula_error(std::string_view msg) = 0;
+    virtual void push_token(fopcode_t fop) = 0;
+    virtual void push_value(double val) = 0;
+    virtual void push_string(size_t sid) = 0;
+    virtual void push_single_ref(const address_t& addr, const abs_address_t& pos) = 0;
+    virtual void push_range_ref(const range_t& range, const abs_address_t& pos) = 0;
+    virtual void push_table_ref(const table_t& table) = 0;
+    virtual void push_function(formula_function_t foc) = 0;
+};
+
+}}
+
+#endif
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/interface/table_handler.hpp b/include/ixion/interface/table_handler.hpp
new file mode 100644
index 0000000..0971d2e
--- /dev/null
+++ b/include/ixion/interface/table_handler.hpp
@@ -0,0 +1,63 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef IXION_INTERFACE_TABLE_HANDLER_HPP
+#define IXION_INTERFACE_TABLE_HANDLER_HPP
+
+#include "../types.hpp"
+
+namespace ixion {
+
+struct abs_address_t;
+struct abs_range_t;
+
+namespace iface {
+
+class IXION_DLLPUBLIC table_handler
+{
+public:
+    virtual ~table_handler();
+
+    /**
+     * Get the data range associated with a given column name.  The current
+     * position is used to infer which table to use.
+     *
+     * @param pos current cell position.
+     * @param column_first name of the starting column within the table.
+     * @param column_last name of the ending column within the table, or
+     *                    empty_string_id if it's a single column.
+     * @param areas area specifiter value, which may consist of one or more
+     *              values of table_area_t.
+     *
+     * @return referenced data range.
+     */
+    virtual abs_range_t get_range(
+        const abs_address_t& pos, string_id_t column_first, string_id_t column_last,
+        table_areas_t areas) const = 0;
+
+    /**
+     * Get the data range associated with given table and column names.
+     *
+     * @param table string identifier representing the table name.
+     * @param column_first name of the starting column within the table.
+     * @param column_last name of the ending column within the table, or
+     *                    empty_string_id if it's a single column.
+     * @param areas area specifiter value, which may consist of one or more
+     *              values of table_area_t.
+     *
+     * @return referenced data range.
+     */
+    virtual abs_range_t get_range(
+        string_id_t table, string_id_t column_first, string_id_t column_last,
+        table_areas_t areas) const = 0;
+};
+
+}}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/macros.hpp b/include/ixion/macros.hpp
new file mode 100644
index 0000000..1ac84c1
--- /dev/null
+++ b/include/ixion/macros.hpp
@@ -0,0 +1,18 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef __IXION_MACROS_HPP__
+#define __IXION_MACROS_HPP__
+
+/**
+ * Use this macro with a literal string and it returns the literal string
+ * followed by its length.
+ */
+#define IXION_ASCII(literal) literal, sizeof(literal)-1
+
+#endif
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/matrix.hpp b/include/ixion/matrix.hpp
new file mode 100644
index 0000000..d001f92
--- /dev/null
+++ b/include/ixion/matrix.hpp
@@ -0,0 +1,122 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_MATRIX_HPP
+#define INCLUDED_IXION_MATRIX_HPP
+
+#include "types.hpp"
+
+#include <memory>
+#include <vector>
+#include <string>
+#include <variant>
+
+namespace ixion {
+
+class numeric_matrix;
+
+/**
+ * 2-dimensional matrix consisting of elements of variable types.  Each
+ * element can be numeric, string, or empty.  This class is used to
+ * represent range values or in-line matrices.
+ */
+class IXION_DLLPUBLIC matrix
+{
+    struct impl;
+    std::unique_ptr<impl> mp_impl;
+
+public:
+
+    enum class element_type { numeric, string, boolean, error, empty };
+
+    struct element
+    {
+        using value_type = std::variant<double, bool, std::string_view, formula_error_t>;
+
+        element_type type;
+        value_type value;
+    };
+
+    matrix();
+    matrix(size_t rows, size_t cols);
+    matrix(size_t rows, size_t cols, double numeric);
+    matrix(size_t rows, size_t cols, bool boolean);
+    matrix(size_t rows, size_t cols, const std::string& str);
+    matrix(size_t rows, size_t cols, formula_error_t error);
+    matrix(const matrix& other);
+    matrix(matrix&& other);
+    matrix(const numeric_matrix& other);
+    ~matrix();
+
+    matrix& operator= (matrix other);
+
+    /**
+     * Determine if the entire matrix consists only of numeric value elements.
+     *
+     * @return true if the entire matrix consits only of numeric value
+     *         elements, false otherwise.
+     */
+    bool is_numeric() const;
+
+    bool get_boolean(size_t row, size_t col) const;
+    bool is_numeric(size_t row, size_t col) const;
+    double get_numeric(size_t row, size_t col) const;
+    void set(size_t row, size_t col, double val);
+    void set(size_t row, size_t col, bool val);
+    void set(size_t row, size_t col, const std::string& str);
+    void set(size_t row, size_t col, formula_error_t val);
+
+    element get(size_t row, size_t col) const;
+
+    size_t row_size() const;
+    size_t col_size() const;
+
+    void swap(matrix& r);
+
+    numeric_matrix as_numeric() const;
+
+    bool operator== (const matrix& r) const;
+    bool operator!= (const matrix& r) const;
+};
+
+class IXION_DLLPUBLIC numeric_matrix
+{
+    friend class matrix;
+
+    struct impl;
+    std::unique_ptr<impl> mp_impl;
+
+public:
+    numeric_matrix();
+    numeric_matrix(size_t rows, size_t cols);
+
+    /**
+     * Constructor with initial values.
+     *
+     * @param array  Array of initial values stored in column-major order.
+     * @param rows Number of rows.
+     * @param cols Number of columns.
+     */
+    numeric_matrix(std::vector<double> array, size_t rows, size_t cols);
+    numeric_matrix(numeric_matrix&& r);
+    ~numeric_matrix();
+
+    numeric_matrix& operator= (numeric_matrix other);
+
+    double& operator() (size_t row, size_t col);
+    const double& operator() (size_t row, size_t col) const;
+
+    void swap(numeric_matrix& r);
+
+    size_t row_size() const;
+    size_t col_size() const;
+};
+
+}
+
+#endif
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/model_context.hpp b/include/ixion/model_context.hpp
new file mode 100644
index 0000000..b9d0987
--- /dev/null
+++ b/include/ixion/model_context.hpp
@@ -0,0 +1,446 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_MODEL_CONTEXT_HPP
+#define INCLUDED_IXION_MODEL_CONTEXT_HPP
+
+#include "env.hpp"
+#include "formula_tokens_fwd.hpp"
+#include "types.hpp"
+
+#include <string>
+#include <memory>
+#include <variant>
+
+namespace ixion {
+
+class cell_access;
+class dirty_cell_tracker;
+class formula_cell;
+class formula_name_resolver;
+class formula_result;
+class matrix;
+class model_iterator;
+class named_expressions_iterator;
+struct abs_address_t;
+struct abs_range_t;
+struct abs_rc_range_t;
+struct config;
+struct named_expression_t;
+
+namespace iface {
+
+class session_handler;
+class table_handler;
+
+}
+
+namespace detail {
+
+class model_context_impl;
+
+}
+
+/**
+ * This class stores all data relevant to current session.  You can think of
+ * this like a document model for each formula calculation run.  Note that
+ * only those methods called from the formula interpreter are specified in
+ * the interface; this explains why accessors for the most part only have
+ * the 'get' method not paired with its 'set' counterpart.
+ */
+class IXION_DLLPUBLIC model_context final
+{
+    friend class named_expressions_iterator;
+    friend class cell_access;
+
+    std::unique_ptr<detail::model_context_impl> mp_impl;
+
+public:
+    class IXION_DLLPUBLIC session_handler_factory
+    {
+    public:
+        virtual std::unique_ptr<iface::session_handler> create();
+        virtual ~session_handler_factory();
+    };
+
+    /**
+     * Cell value only to be used to input a collection of cells to sheet.
+     * Formula cells are not supported.
+     */
+    struct IXION_DLLPUBLIC input_cell
+    {
+        using value_type = std::variant<bool, double, std::string_view>;
+
+        celltype_t type;
+        value_type value;
+
+        /** Initializes the cell to be empty. */
+        input_cell(std::nullptr_t);
+        /** Boolean cell value. */
+        input_cell(bool b);
+        /** The char array must be null-terminated. */
+        input_cell(const char* s);
+        /** Numeric cell value. */
+        input_cell(double v);
+
+        input_cell(const input_cell& other);
+    };
+
+    class IXION_DLLPUBLIC input_row
+    {
+        std::initializer_list<input_cell> m_cells;
+    public:
+        input_row(std::initializer_list<input_cell> cells);
+
+        const std::initializer_list<input_cell>& cells() const;
+    };
+
+    model_context();
+    model_context(const rc_size_t& sheet_size);
+    ~model_context();
+
+    /**
+     * Query the current policy on what to do when a formula cell result is
+     * being requested while the result has not yet been computed.
+     */
+    formula_result_wait_policy_t get_formula_result_wait_policy() const;
+
+    /**
+     * This method is used to notify the model access implementer of formula
+     * events.
+     *
+     * @param event event type.
+     */
+    void notify(formula_event_t event);
+
+    const config& get_config() const;
+    dirty_cell_tracker& get_cell_tracker();
+    const dirty_cell_tracker& get_cell_tracker() const;
+
+    bool is_empty(const abs_address_t& addr) const;
+    bool is_empty(const abs_range_t& range) const;
+    celltype_t get_celltype(const abs_address_t& addr) const;
+    cell_value_t get_cell_value_type(const abs_address_t& addr) const;
+
+    /**
+     * Get a numeric representation of the cell value at specified position.
+     * If the cell at the specified position is a formula cell and its result
+     * has not yet been computed, it will block until the result becomes
+     * available.
+     *
+     * @param addr position of the cell.
+     *
+     * @return numeric representation of the cell value.
+     */
+    double get_numeric_value(const abs_address_t& addr) const;
+    bool get_boolean_value(const abs_address_t& addr) const;
+    string_id_t get_string_identifier(const abs_address_t& addr) const;
+
+    /**
+     * Get a string value associated with the cell at the specified position.
+     * It returns a valid string value only when the cell is a string cell, or
+     * is a formula cell containing a string result.  Otherwise, it returns a
+     * nullptr.
+     *
+     * @param addr position of the cell.
+     *
+     * @return pointer to a string value if the cell stores a valid string
+     *         value, else nullptr.
+     */
+    std::string_view get_string_value(const abs_address_t& addr) const;
+    const formula_cell* get_formula_cell(const abs_address_t& addr) const;
+    formula_cell* get_formula_cell(const abs_address_t& addr);
+
+    formula_result get_formula_result(const abs_address_t& addr) const;
+
+    /**
+     * Get a named expression token set associated with specified name if
+     * present.  It first searches the local sheet scope for the name, then if
+     * it's not present, it searches the global scope.
+     *
+     * @param sheet index of the sheet scope to search in.
+     * @param name name of the expression.
+     *
+     * @return const pointer to the token set if exists, nullptr otherwise.
+     */
+    const named_expression_t* get_named_expression(sheet_t sheet, std::string_view name) const;
+
+    double count_range(const abs_range_t& range, values_t values_type) const;
+
+    /**
+     * Obtain range value in matrix form.  Multi-sheet ranges are not
+     * supported.  If the specified range consists of multiple sheets, it
+     * throws an exception.
+     *
+     * @param range absolute, single-sheet range address.  Multi-sheet ranges
+     *              are not allowed.
+     *
+     * @return range value represented as matrix.
+     */
+    matrix get_range_value(const abs_range_t& range) const;
+
+    /**
+     * Session handler instance receives various events from the formula
+     * interpretation run, in order to respond to those events.  This is
+     * optional; the model context implementation is not required to provide a
+     * handler.
+     *
+     * @return a new session handler instance.  It may be nullptr.
+     */
+    std::unique_ptr<iface::session_handler> create_session_handler();
+
+    /**
+     * Table interface provides access to all table ranges stored in the
+     * document model.  A table is a 2-dimensional range of cells that include
+     * named columns.  It is used when resolving a table reference that refers
+     * to a cell or a range of cells by the table name and/or column name.
+     *
+     * @return non-null pointer to the table storage inside the model, or
+     *         nullptr if no table is present or supported by the model
+     *         implementation.
+     */
+    iface::table_handler* get_table_handler();
+    const iface::table_handler* get_table_handler() const;
+
+    /**
+     * Try to add a new string to the string pool. If the same string already
+     * exists in the pool, the new string won't be added to the pool.
+     *
+     * @param s string to try to add to the pool.
+     *
+     * @return string_id_t integer value representing the string.
+     */
+    string_id_t add_string(std::string_view s);
+    const std::string* get_string(string_id_t identifier) const;
+
+    /**
+     * Get the index of sheet from sheet name.  If the sheet name doesn't exist,
+     * it returns a value equal to <code>ixion::invalid_sheet</code>.
+     *
+     * @param name sheet name.
+     *
+     * @return 0-based sheet index, or <code>ixion::invalid_sheet</code> in case
+     *         the document doesn't have a sheet by the specified name.
+     */
+    sheet_t get_sheet_index(std::string_view name) const;
+    std::string get_sheet_name(sheet_t sheet) const;
+
+    /**
+     * Set a new name to an existing sheet.
+     *
+     * @param sheet 0-based sheet index.
+     * @param name New name of a sheet.
+     */
+    void set_sheet_name(sheet_t sheet, std::string name);
+
+    /**
+     * Get the size of a sheet.
+     *
+     * @return sheet size.
+     */
+    rc_size_t get_sheet_size() const;
+
+    /**
+     * Return the number of sheets.
+     *
+     * @return number of sheets.
+     */
+    size_t get_sheet_count() const;
+
+    string_id_t append_string(std::string_view s);
+
+    void set_sheet_size(const rc_size_t& sheet_size);
+    void set_config(const config& cfg);
+
+    void empty_cell(const abs_address_t& addr);
+
+    void set_numeric_cell(const abs_address_t& addr, double val);
+    void set_boolean_cell(const abs_address_t& adr, bool val);
+    void set_string_cell(const abs_address_t& addr, std::string_view s);
+    void set_string_cell(const abs_address_t& addr, string_id_t identifier);
+
+    cell_access get_cell_access(const abs_address_t& addr) const;
+
+    /**
+     * Duplicate the value of the source cell to one or more cells located
+     * immediately below it.
+     *
+     * @param src position of the source cell to copy the value from.
+     * @param n_dst number of cells below to copy the value to.  It must be at
+     *              least one.
+     */
+    void fill_down_cells(const abs_address_t& src, size_t n_dst);
+
+    /**
+     * Set a formula cell at a specified address.
+     *
+     * @param addr address at which to set a formula cell.
+     * @param tokens formula tokens to put into the formula cell.
+     *
+     * @return pointer to the formula cell instance inserted into the model.
+     */
+    formula_cell* set_formula_cell(const abs_address_t& addr, formula_tokens_t tokens);
+
+    /**
+     * Set a formula cell at a specified address.  This variant takes a
+     * formula tokens store that can be shared between multiple formula cell
+     * instances.
+     *
+     * @param addr address at which to set a formula cell.
+     * @param tokens formula tokens to put into the formula cell.
+     *
+     * @return pointer to the formula cell instance inserted into the model.
+     */
+    formula_cell* set_formula_cell(const abs_address_t& addr, const formula_tokens_store_ptr_t& tokens);
+
+    /**
+     * Set a formula cell at a specified address.  This variant takes a
+     * formula tokens store that can be shared between multiple formula cell
+     * instances.
+     *
+     * @param addr address at which to set a formula cell.
+     * @param tokens formula tokens to put into the formula cell.
+     * @param result cached result of this formula cell.
+     *
+     * @return pointer to the formula cell instance inserted into the model.
+     */
+    formula_cell* set_formula_cell(const abs_address_t& addr, const formula_tokens_store_ptr_t& tokens, formula_result result);
+
+    void set_grouped_formula_cells(const abs_range_t& group_range, formula_tokens_t tokens);
+
+    void set_grouped_formula_cells(const abs_range_t& group_range, formula_tokens_t tokens, formula_result result);
+
+    abs_range_t get_data_range(sheet_t sheet) const;
+
+    /**
+     * Set a named expression associated with a string name in the global
+     * scope.
+     *
+     * @param name name of the expression.
+     * @param expr formula tokens to use for the named expression.
+     */
+    void set_named_expression(std::string name, formula_tokens_t expr);
+
+    /**
+     * Set a named expression associated with a string name in the global
+     * scope.
+     *
+     * @param name name of the expression.
+     * @param origin position of the origin cell.  Origin cell is relevant
+     *               only when you need to convert the tokens into a string
+     *               representation.
+     * @param expr formula tokens to use for the named expression.
+     */
+    void set_named_expression(std::string name, const abs_address_t& origin, formula_tokens_t expr);
+
+    /**
+     * Set a named expression associated with a string name in a sheet-local
+     * scope.
+     *
+     * @param sheet 0-based index of the sheet to register this expression
+     *              with.
+     * @param name name of the expression.
+     * @param expr formula tokens to use for the named expression.
+     */
+    void set_named_expression(sheet_t sheet, std::string name, formula_tokens_t expr);
+
+    /**
+     * Set a named expression associated with a string name in a sheet-local
+     * scope.
+     *
+     * @param sheet 0-based index of the sheet to register this expression
+     *              with.
+     * @param name name of the expression.
+     * @param origin position of the origin cell.  Origin cell is relevant
+     *               only when you need to convert the tokens into a string
+     *               representation.
+     * @param expr formula tokens to use for the named expression.
+     */
+    void set_named_expression(sheet_t sheet, std::string name, const abs_address_t& origin, formula_tokens_t expr);
+
+    /**
+     * Append a new sheet to the model.  The caller must ensure that the name
+     * of the new sheet is unique within the model context.  When the name
+     * being used for the new sheet already exists, it throws a
+     * model_context_error exception.
+     *
+     * @param name name of the sheet to be inserted.
+     *
+     * @return sheet index of the inserted sheet.
+     *
+     * @throw model_context_error
+     */
+    sheet_t append_sheet(std::string name);
+
+    /**
+     * A convenient way to mass-insert a range of cell values.  You can
+     * use a nested initializet list representing a range of cell values.  The
+     * outer list represents rows.
+     *
+     * @param sheet sheet index.
+     * @param rows nested list of cell values.  The outer list represents
+     *             rows.
+     */
+    void set_cell_values(sheet_t sheet, std::initializer_list<input_row> rows);
+
+    void set_session_handler_factory(session_handler_factory* factory);
+
+    void set_table_handler(iface::table_handler* handler);
+
+    size_t get_string_count() const;
+
+    void dump_strings() const;
+
+    /**
+     * Get an integer string ID from a string value.  If the string value
+     * doesn't exist in the pool, the value equal to empty_string_id gets
+     * returned.
+     *
+     * @param s string value.
+     *
+     * @return string_id_t integer string ID associated with the string value
+     *         given.
+     */
+    string_id_t get_identifier_from_string(std::string_view s) const;
+
+    /**
+     * Get an immutable iterator that lets you iterate cell values in one
+     * sheet one at a time.  <i>The caller has to ensure that the model
+     * content does not change for the duration of the iteration.</i>
+     *
+     * @param sheet sheet index.
+     * @param dir direction of the iteration.
+     * @param range range on the specified sheet to iterate over.
+     *
+     * @return model iterator instance.
+     */
+    model_iterator get_model_iterator(
+        sheet_t sheet, rc_direction_t dir, const abs_rc_range_t& range) const;
+
+    /**
+     * Get an iterator for global named expressions.
+     */
+    named_expressions_iterator get_named_expressions_iterator() const;
+
+    /**
+     * Get an interator for sheet-local named expressions.
+     *
+     * @param sheet 0-based index of the sheet where the named expressions are
+     *              stored.
+     */
+    named_expressions_iterator get_named_expressions_iterator(sheet_t sheet) const;
+
+    void walk(
+        sheet_t sheet, const abs_rc_range_t& range, column_block_callback_t cb) const;
+
+    bool empty() const;
+};
+
+}
+
+#endif
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/model_iterator.hpp b/include/ixion/model_iterator.hpp
new file mode 100644
index 0000000..dcebc8c
--- /dev/null
+++ b/include/ixion/model_iterator.hpp
@@ -0,0 +1,76 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_MODEL_ITERATOR_HPP
+#define INCLUDED_IXION_MODEL_ITERATOR_HPP
+
+#include "types.hpp"
+
+#include <memory>
+#include <iosfwd>
+#include <variant>
+
+namespace ixion {
+
+namespace detail { class model_context_impl; }
+class formula_cell;
+struct abs_rc_range_t;
+
+class IXION_DLLPUBLIC model_iterator
+{
+public:
+    class impl;
+
+private:
+    friend class detail::model_context_impl;
+    std::unique_ptr<model_iterator::impl> mp_impl;
+
+    model_iterator(const detail::model_context_impl& cxt, sheet_t sheet, const abs_rc_range_t& range, rc_direction_t dir);
+public:
+
+    struct IXION_DLLPUBLIC cell
+    {
+        using value_type = std::variant<bool, double, string_id_t, const formula_cell*>;
+
+        row_t row;
+        col_t col;
+        celltype_t type;
+        value_type value;
+
+        cell();
+        cell(row_t _row, col_t _col);
+        cell(row_t _row, col_t _col, bool _b);
+        cell(row_t _row, col_t _col, string_id_t _s);
+        cell(row_t _row, col_t _col, double _v);
+        cell(row_t _row, col_t _col, const formula_cell* _f);
+
+        bool operator== (const cell& other) const;
+        bool operator!= (const cell& other) const;
+    };
+
+    model_iterator();
+    model_iterator(const model_iterator&) = delete;
+    model_iterator(model_iterator&& other);
+    ~model_iterator();
+
+    model_iterator& operator= (const model_iterator&) = delete;
+    model_iterator& operator= (model_iterator&& other);
+
+    bool has() const;
+
+    void next();
+
+    const cell& get() const;
+};
+
+IXION_DLLPUBLIC std::ostream& operator<< (std::ostream& os, const model_iterator::cell& c);
+
+} // namespace ixion
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/module.hpp b/include/ixion/module.hpp
new file mode 100644
index 0000000..3f0fbc2
--- /dev/null
+++ b/include/ixion/module.hpp
@@ -0,0 +1,37 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_MODULE_HPP
+#define INCLUDED_IXION_MODULE_HPP
+
+#include "env.hpp"
+
+namespace ixion { namespace draft {
+
+/**
+ * Initialize modules if exists.
+ */
+IXION_DLLPUBLIC void init_modules();
+
+IXION_DLLPUBLIC void unload_module(void* handler);
+
+class compute_engine;
+
+using create_compute_engine_t = compute_engine* (*)();
+using destroy_compute_engine_t = void (*)(const compute_engine*);
+
+struct module_def
+{
+    create_compute_engine_t create_compute_engine;
+    destroy_compute_engine_t destroy_compute_engine;
+};
+
+}}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/named_expressions_iterator.hpp b/include/ixion/named_expressions_iterator.hpp
new file mode 100644
index 0000000..7511fef
--- /dev/null
+++ b/include/ixion/named_expressions_iterator.hpp
@@ -0,0 +1,57 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_NAMED_EXPRESSIONS_ITERATOR_HPP
+#define INCLUDED_IXION_NAMED_EXPRESSIONS_ITERATOR_HPP
+
+#include "types.hpp"
+#include "formula_tokens_fwd.hpp"
+
+#include <memory>
+#include <iosfwd>
+#include <string>
+
+namespace ixion {
+
+class model_context;
+struct abs_address_t;
+
+class IXION_DLLPUBLIC named_expressions_iterator
+{
+    friend class model_context;
+
+    struct impl;
+    std::unique_ptr<impl> mp_impl;
+
+    named_expressions_iterator(const model_context& cxt, sheet_t scope);
+
+public:
+    named_expressions_iterator();
+    named_expressions_iterator(const named_expressions_iterator& other);
+    named_expressions_iterator(named_expressions_iterator&& other);
+    ~named_expressions_iterator();
+
+    struct named_expression
+    {
+        const std::string* name;
+        const named_expression_t* expression;
+    };
+
+    size_t size() const;
+    bool has() const;
+    void next();
+
+    named_expression get() const;
+
+    named_expressions_iterator& operator= (const named_expressions_iterator& other);
+};
+
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/table.hpp b/include/ixion/table.hpp
new file mode 100644
index 0000000..c0e556e
--- /dev/null
+++ b/include/ixion/table.hpp
@@ -0,0 +1,34 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_TABLE_HPP
+#define INCLUDED_IXION_TABLE_HPP
+
+#include "types.hpp"
+
+namespace ixion {
+
+struct IXION_DLLPUBLIC table_t
+{
+    string_id_t name;
+    string_id_t column_first;
+    string_id_t column_last;
+    table_areas_t areas;
+
+    table_t();
+
+    bool operator== (const table_t& r) const;
+    bool operator!= (const table_t& r) const;
+};
+
+IXION_DLLPUBLIC std::ostream& operator<<(std::ostream& os, const table_t& table);
+
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/include/ixion/types.hpp b/include/ixion/types.hpp
new file mode 100644
index 0000000..5933646
--- /dev/null
+++ b/include/ixion/types.hpp
@@ -0,0 +1,373 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_IXION_TYPES_HPP
+#define INCLUDED_IXION_TYPES_HPP
+
+#include "env.hpp"
+
+#include <cstdlib>
+#include <cstdint>
+#include <string_view>
+#include <functional>
+
+namespace ixion {
+
+/** Column index type. */
+using col_t = int32_t;
+
+/** Row index type. */
+using row_t = int32_t;
+
+/** Sheet index type.*/
+using sheet_t = int32_t;
+
+/**
+ * Integer type that is large enough to store either a row or a column
+ * index.
+ */
+using rc_t = row_t;
+
+/**
+ * String ID type.
+ *
+ * All string values are converted into integer tokens. You need to call the
+ * get_string() method of ixion::model_context to get the
+ * actual string value.
+ */
+using string_id_t = uint32_t;
+
+/**
+ * Special sheet ID that represents a global scope, as opposed to a
+ * sheet-local scope.
+ */
+IXION_DLLPUBLIC_VAR const sheet_t global_scope;
+
+/**
+ * Special sheet ID that represents an invalid sheet.
+ */
+IXION_DLLPUBLIC_VAR const sheet_t invalid_sheet;
+
+/**
+ * Determine whether or not a given sheet index is valid.
+ *
+ * @param sheet sheet index to test.
+ *
+ * @return true if the sheet index is valid, false otherwise.
+ */
+IXION_DLLPUBLIC bool is_valid_sheet(sheet_t sheet);
+
+/** Global string ID representing an empty string. */
+IXION_DLLPUBLIC_VAR const string_id_t empty_string_id;
+
+/**
+ * This type represents a raw cell type as stored in ixion::model_context.
+ */
+enum class celltype_t : uint8_t
+{
+    /** unknown cell type.*/
+    unknown = 0,
+    /** cell contains a raw string value.*/
+    string,
+    /** cell contains a raw numeric value.*/
+    numeric,
+    /** cell contains a formula object. */
+    formula,
+    /** cell contains a raw boolean value. */
+    boolean,
+    /** cell is empty and contains absolutely nothing. */
+    empty
+};
+
+/**
+ * Similar to celltype_t, except that it does not include a formula type.
+ * Instead it uses the formula result type to classify its type. The error
+ * type refers to an error value in formula cell.
+ */
+enum class cell_value_t : uint8_t
+{
+    /** unknown cell value type. */
+    unknown = 0,
+    /**
+     * either the cell contains a raw string value, or a calculated formula
+     * cell whose result is of string type.
+     */
+    string,
+    /**
+     * either the cell contains a raw numeric value, or a calculated formula
+     * cell whose result is of numeric type.
+     */
+    numeric,
+    /**
+     * this type corresponds with a formula cell whose result contains an
+     * error.
+     */
+    error,
+    /**
+     * either the cell contains a raw boolean value type, or a calculated
+     * formula cell whose result is of boolean type.
+     */
+    boolean,
+    /**
+     * the cell is empty and contains nothing whatsoever.
+     */
+    empty
+};
+
+enum value_t
+{
+    value_none    = 0x00,
+    value_string  = 0x01,
+    value_numeric = 0x02,
+    value_boolean = 0x04,
+    value_empty   = 0x08
+};
+
+/** type that stores a mixture of value_t values. */
+class values_t
+{
+    int m_val;
+public:
+    values_t(int val) : m_val(val) {}
+    bool is_numeric() const { return (m_val & value_numeric) == value_numeric; }
+    bool is_boolean() const { return (m_val & value_boolean) == value_boolean; }
+    bool is_string() const { return (m_val & value_string) == value_string; }
+    bool is_empty() const { return (m_val & value_empty) == value_empty; }
+};
+
+/** Value that specifies the area inside a table. */
+enum table_area_t
+{
+    table_area_none    = 0x00,
+    table_area_data    = 0x01,
+    table_area_headers = 0x02,
+    table_area_totals  = 0x04,
+    table_area_all     = 0x07
+};
+
+/** type that stores a mixture of ixion::table_area_t values. */
+using table_areas_t = int32_t;
+
+/**
+ * Formula name resolver type specifies how name tokens are resolved.
+ */
+enum class formula_name_resolver_t
+{
+    /** Unknown syntax. */
+    unknown    = 0,
+    /** Default A1 syntax used in Excel */
+    excel_a1   = 1,
+    /** R1C1 syntax available in Excel */
+    excel_r1c1 = 2,
+    /** Default A1 syntax used in Calc */
+    calc_a1    = 3,
+    /** OpenFormula syntax */
+    odff       = 4,
+    /** ODF cell-range-address syntax */
+    odf_cra    = 5,
+};
+
+/**
+ * Formula error types.  Note that only the official (i.e. non-internal)
+ * error types have their corresponding error strings.  Use the
+ * get_formula_error_name() function to convert an enum member value of this
+ * type to its string representation.
+ */
+enum class formula_error_t : uint8_t
+{
+    no_error                 = 0,
+    ref_result_not_available = 1,
+    division_by_zero         = 2,
+    invalid_expression       = 3,
+    name_not_found           = 4,
+    no_range_intersection    = 5,
+    invalid_value_type       = 6,
+    no_value_available       = 7,
+
+    no_result_error          = 253, // internal only error
+    stack_error              = 254, // internal only error
+    general_error            = 255, // internal only error
+};
+
+/**
+ * Type of policy on what to do when querying for the result of a formula
+ * cell whose result has not yet been calculated.
+ */
+enum class formula_result_wait_policy_t
+{
+    /**
+     * Querying for the result of a formula cell will block until the
+     * calculation is complete.
+     */
+    block_until_done,
+
+    /**
+     * Querying for the result of a formula cell that has not yet been
+     * calculated will throw an exception.
+     */
+    throw_exception,
+};
+
+/**
+ * Formula event type used for event notification during calculation of
+ * formula cells.
+ *
+ * @see ixion::model_context::notify
+ */
+enum class formula_event_t
+{
+    /** Start of the calculations of formula cells. */
+    calculation_begins,
+    /** End of the calculations of formula cells. */
+    calculation_ends,
+};
+
+/**
+ * Specifies iterator direction of a ixion::model_context.
+ */
+enum class rc_direction_t
+{
+    /** Flows left to right first then top to bottom. */
+    horizontal,
+    /** Flows top to bottom first then left to right. */
+    vertical
+};
+
+/**
+ * This structure stores a 2-dimensional size information.
+ */
+struct IXION_DLLPUBLIC rc_size_t
+{
+    row_t row;
+    col_t column;
+
+    rc_size_t();
+    rc_size_t(const rc_size_t& other);
+    rc_size_t(row_t _row, col_t _column);
+    ~rc_size_t();
+
+    rc_size_t& operator= (const rc_size_t& other);
+};
+
+/**
+ * This strcuture stores information about grouped formula cells.  All
+ * formula cells belonging to the same group shares the same set of values.
+ */
+struct IXION_DLLPUBLIC formula_group_t
+{
+    /** Size of the formula group. */
+    rc_size_t size;
+    /**
+     * Unique value identifying the group a cell belongs to.  Cells belonging
+     * to the same formula group should have the same value.
+     */
+    uintptr_t identity;
+    /** Boolean value indicating whether or not a cell is grouped.   */
+    bool grouped;
+
+    formula_group_t();
+    formula_group_t(const formula_group_t& r);
+    formula_group_t(const rc_size_t& _group_size, uintptr_t _identity, bool _grouped);
+    ~formula_group_t();
+
+    formula_group_t& operator= (const formula_group_t& other);
+};
+
+/**
+ * Get a string representation of a formula error type.
+ *
+ * @param fe enum value representing a formula error type.
+ * @return null-terminated string representation of the formula error type.
+ */
+IXION_DLLPUBLIC std::string_view get_formula_error_name(formula_error_t fe);
+
+/**
+ * Parse a formula error string and convert it to a corresponding enum value.
+ *
+ * @param s string representation of a formula error type.
+ * @return enum value for a formula error type.
+ */
+IXION_DLLPUBLIC formula_error_t to_formula_error_type(std::string_view s);
+
+using column_block_handle = void*;
+
+/**
+ * Type of a column block that stores a series of adjacent cell values of the
+ * same type.
+ */
+enum class column_block_t : int
+{
+    unknown = 0,
+    empty,
+    boolean,
+    numeric,
+    string,
+    formula
+};
+
+/**
+ * Data that represents the shape of a column block.
+ */
+struct IXION_DLLPUBLIC column_block_shape_t
+{
+    std::size_t position;
+    std::size_t size;
+    std::size_t offset;
+    column_block_t type;
+    column_block_handle data;
+
+    column_block_shape_t();
+
+    column_block_shape_t(
+        std::size_t _position, std::size_t _size, std::size_t _offset,
+        column_block_t _type, column_block_handle _data);
+
+    column_block_shape_t(const column_block_shape_t& other);
+
+    column_block_shape_t& operator=(const column_block_shape_t& other);
+};
+
+/**
+ * Callback function type to be used during traversal of column data.
+ */
+using column_block_callback_t = std::function<bool(col_t, row_t, row_t, const column_block_shape_t&)>;
+
+IXION_DLLPUBLIC std::ostream& operator<< (std::ostream& os, const column_block_shape_t& v);
+
+/**
+ * Specifies how to determine whether or not to display a sheet name of a cell
+ * or range reference.
+ */
+enum class display_sheet_t
+{
+    /** Sheet name display preference is not specified. */
+    unspecified,
+    /** Sheet name should be always displayed. */
+    always,
+    /** Sheet name should never be displayed. */
+    never,
+    /**
+     * Sheet name should be displayed only when the sheet index of a reference
+     * is different from that of the position of a referencing cell.
+     */
+    only_if_different,
+};
+
+struct IXION_DLLPUBLIC print_config
+{
+    display_sheet_t display_sheet = display_sheet_t::only_if_different;
+
+    print_config();
+    print_config(const print_config& other);
+    ~print_config();
+};
+
+} // namespace ixion
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */