1 files changed, 318 insertions, 0 deletions
diff --git a/src/boost/libs/metaparse/example/constexpr_parser/main.cpp b/src/boost/libs/metaparse/example/constexpr_parser/main.cpp
new file mode 100644
index 000000000..4fe291b07
--- /dev/null
+++ b/src/boost/libs/metaparse/example/constexpr_parser/main.cpp
@@ -0,0 +1,318 @@
+// Copyright Abel Sinkovics (abel@sinkovics.hu)  2012.
+// Distributed under the Boost Software License, Version 1.0.
+//    (See accompanying file LICENSE_1_0.txt or copy at
+//          http://www.boost.org/LICENSE_1_0.txt)
+
+#include <boost/metaparse/sequence.hpp>
+#include <boost/metaparse/lit_c.hpp>
+#include <boost/metaparse/foldl.hpp>
+#include <boost/metaparse/entire_input.hpp>
+#include <boost/metaparse/string.hpp>
+#include <boost/metaparse/build_parser.hpp>
+#include <boost/metaparse/get_result.hpp>
+#include <boost/metaparse/start.hpp>
+#include <boost/metaparse/last_of.hpp>
+#include <boost/metaparse/iterate_c.hpp>
+#include <boost/metaparse/one_char.hpp>
+#include <boost/metaparse/return_.hpp>
+
+#include <boost/mpl/apply_wrap.hpp>
+#include <boost/mpl/at.hpp>
+#include <boost/mpl/int.hpp>
+#include <boost/mpl/plus.hpp>
+#include <boost/mpl/front.hpp>
+#include <boost/mpl/pop_front.hpp>
+#include <boost/mpl/size.hpp>
+
+#include <iostream>
+#include <string>
+
+#if BOOST_METAPARSE_STD < 2011
+
+int main()
+{
+  std::cout
+    << "This example focuses on constexpr, which is not supported"
+    << std::endl;
+}
+
+#else
+
+using boost::metaparse::sequence;
+using boost::metaparse::lit_c;
+using boost::metaparse::build_parser;
+using boost::metaparse::foldl;
+using boost::metaparse::entire_input;
+using boost::metaparse::get_result;
+using boost::metaparse::start;
+using boost::metaparse::last_of;
+using boost::metaparse::iterate_c;
+using boost::metaparse::one_char;
+using boost::metaparse::return_;
+
+using boost::mpl::apply_wrap1;
+using boost::mpl::apply_wrap2;
+using boost::mpl::plus;
+using boost::mpl::int_;
+using boost::mpl::at_c;
+using boost::mpl::front;
+using boost::mpl::pop_front;
+using boost::mpl::size;
+
+using std::ostream;
+
+/*
+ * The grammar
+ *
+ * S ::= a* b* a*
+ */
+
+struct parsed
+{
+  template <class T>
+  constexpr static parsed build()
+  {
+    return
+      parsed(
+        at_c<typename T::type, 0>::type::value,
+        at_c<typename T::type, 1>::type::value,
+        at_c<typename T::type, 2>::type::value
+      );
+  }
+
+  constexpr parsed(int a1, int b, int a2) :
+    a_count1(a1),
+    b_count(b),
+    a_count2(a2)
+  {};
+
+  int a_count1;
+  int b_count;
+  int a_count2;
+};
+
+ostream& operator<<(ostream& o, const parsed& p)
+{
+  return
+    o << "(" << p.a_count1 << ", " << p.b_count << ", " << p.a_count2 << ")";
+}
+
+// constexpr parser
+
+template <class T, int Len>
+struct const_list
+{
+  T head;
+  const_list<T, Len - 1> tail;
+
+  constexpr const_list(const T& h, const const_list<T, Len - 1>& t) :
+    head(h),
+    tail(t)
+  {}
+
+  constexpr const_list<T, Len + 1> push_front(const T& t) const
+  {
+    return const_list<T, Len + 1>(t, *this);
+  }
+
+  constexpr T at(int n) const
+  {
+    return n == 0 ? head : tail.at(n - 1);
+  }
+};
+
+template <class T>
+struct const_list<T, 0>
+{
+  constexpr const_list<T, 1> push_front(const T& t) const
+  {
+    return const_list<T, 1>(t, *this);
+  }
+
+  constexpr T at(int) const
+  {
+    return T();
+  }
+};
+
+template <class T, int N, int from = 0>
+struct to_list
+{
+  static constexpr const_list<T, N - from> run(const T (&s)[N])
+  {
+    return const_list<T, N - from>(s[from], to_list<T, N, from + 1>::run(s));
+  }
+};
+
+template <class T, int N>
+struct to_list<T, N, N>
+{
+  static constexpr const_list<T, 0> run(const T (&s)[N])
+  {
+    return const_list<T, 0>();
+  }
+};
+
+struct presult
+{
+  int value;
+  int remaining_from;
+
+  constexpr presult(int v, int r) : value(v), remaining_from(r) {}
+
+  constexpr presult incr() const { return presult(value + 1, remaining_from); }
+};
+
+template <char C, int N>
+constexpr presult parse_cs(const const_list<char, N>& s, int from)
+{
+  return
+    from < N ?
+    (s.at(from) == C ? parse_cs<C, N>(s, from + 1).incr() : presult(0, from)) :
+    presult(0, from);
+}
+
+template <int N>
+constexpr parsed parse_impl(const const_list<char, N>& s)
+{
+  return
+    parsed(
+      parse_cs<'a', N>(s, 0).value,
+      parse_cs<'b', N>(s, parse_cs<'a', N>(s, 0).remaining_from).value,
+      parse_cs<'a', N>(
+        s,
+        parse_cs<'b', N>(
+          s,
+          parse_cs<'a', N>(s, 0).remaining_from
+        ).remaining_from
+      ).value
+    );
+}
+
+template <int N>
+constexpr parsed parse(const char (&s)[N])
+{
+  return parse_impl(to_list<char, N>::run(s));
+}
+
+// TMP parser
+
+struct count
+{
+  typedef count type;
+
+  template <class State, class C>
+  struct apply : plus<int_<1>, State> {};
+};
+
+typedef foldl<lit_c<'a'>, int_<0>, count> as;
+typedef foldl<lit_c<'b'>, int_<0>, count> bs;
+
+typedef sequence<as, bs, as> s;
+
+typedef build_parser<entire_input<s> > parser;
+
+#ifdef P
+  #error P already defined
+#endif
+#define P(x) \
+  parsed::build<boost::mpl::apply_wrap1<parser, BOOST_METAPARSE_STRING(#x)> >()
+
+// Mixed parser
+
+template <class ValueType, class L, int Len>
+struct tmp_to_const_list_impl
+{
+  constexpr static const_list<ValueType, Len> run()
+  {
+    return
+      const_list<ValueType, Len>(
+        front<L>::type::value,
+        tmp_to_const_list_impl<
+          ValueType,
+          typename pop_front<L>::type,
+          Len - 1
+        >::run()
+      );
+  }
+};
+
+template <class ValueType, class L>
+struct tmp_to_const_list_impl<ValueType, L, 0>
+{
+  constexpr static const_list<ValueType, 0> run()
+  {
+    return const_list<ValueType, 0>();
+  }
+};
+
+template <class ValueType, class L>
+struct tmp_to_const_list :
+  tmp_to_const_list_impl<ValueType, L, size<L>::type::value>
+{};
+
+template <char C>
+struct parse_with_constexpr
+{
+  typedef parse_with_constexpr type;
+
+  template <class S>
+  static constexpr presult impl()
+  {
+    return
+      parse_cs<C, size<S>::type::value>(tmp_to_const_list<char, S>::run(), 0);
+  }
+
+  template <class S, class Pos>
+  struct apply :
+    apply_wrap2<
+      last_of<
+        iterate_c<one_char, impl<S>().remaining_from>,
+        return_<int_<impl<S>().value> >
+      >,
+      S,
+      Pos
+    >
+  {};
+};
+
+typedef parse_with_constexpr<'b'> bs_mixed;
+
+typedef sequence<as, bs_mixed, as> s_mixed;
+
+typedef build_parser<entire_input<s_mixed> > parser_mixed;
+
+#ifdef P_MIXED
+  #error P_MIXED already defined
+#endif
+#define P_MIXED(x) \
+  parsed::build< \
+    boost::mpl::apply_wrap1<parser_mixed, BOOST_METAPARSE_STRING(#x)> \
+  >()
+
+int main()
+{
+  using std::cout;
+  using std::endl;
+  
+  cout
+    << "TMP only parsers:" << endl
+    << P(aba) << endl
+    << P(aaaaaaabbbbaaaa) << endl
+    << endl
+
+    << "constexpr only parsers:" << endl
+    << parse("") << endl
+    << parse("aba") << endl
+    << parse("aaaaaaabbbbaaaa") << endl
+    << endl
+
+    << "mixed parsers:" << endl
+    << P_MIXED(aba) << endl
+    << P_MIXED(aaaaaaabbbbaaaa) << endl
+    << endl
+    ;
+}
+
+#endif
+