From 483eb2f56657e8e7f419ab1a4fab8dce9ade8609 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sat, 27 Apr 2024 20:24:20 +0200 Subject: Adding upstream version 14.2.21. Signed-off-by: Daniel Baumann --- src/boost/libs/yap/example/transform_terminals.cpp | 72 ++++++++++++++++++++++ 1 file changed, 72 insertions(+) create mode 100644 src/boost/libs/yap/example/transform_terminals.cpp (limited to 'src/boost/libs/yap/example/transform_terminals.cpp') diff --git a/src/boost/libs/yap/example/transform_terminals.cpp b/src/boost/libs/yap/example/transform_terminals.cpp new file mode 100644 index 00000000..2bab93d6 --- /dev/null +++ b/src/boost/libs/yap/example/transform_terminals.cpp @@ -0,0 +1,72 @@ +// Copyright (C) 2016-2018 T. Zachary Laine +// +// 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) +//[ transform_terminals +#include + + +struct iota_terminal_transform +{ + // Base case. Note that we're not treating placeholders specially for this + // example (they're easy to special-case if necessary). + template + auto operator()(boost::yap::expr_tag, T && t) + { + // Like the std::iota() algorithm, we create replacement int terminals + // with the values index_, index_ + 1, index_ + 2, etc. + return boost::yap::make_terminal(index_++); + } + + // Recursive case: Match any call expression. + template + auto operator()(boost::yap::expr_tag, + CallableExpr callable, Arg &&... arg) + { + // Even though the callable in a call expression is technically a + // terminal, it doesn't make a lot of sense to replace it with an int, + // so we'll only transform the argument subexpressions. + return boost::yap::make_expression( + boost::yap::as_expr(callable), + boost::yap::transform(boost::yap::as_expr(arg), *this)...); + } + + int index_; +}; + +int sum(int a, int b) { return a + b; } + +int main() +{ + { + // This simple sum(8, 8) expression requires both overloads of + // iota_terminal_transform. + auto expr = boost::yap::make_terminal(sum)(8, 8); + assert(evaluate(expr) == 16); + + auto iota_expr = boost::yap::transform(expr, iota_terminal_transform{1}); + assert(evaluate(iota_expr) == 3); + } + + { + // This expression requires only the terminal case of + // iota_terminal_transform. + auto expr = -(boost::yap::make_terminal(8) + 8); + assert(evaluate(expr) == -16); + + auto iota_expr = boost::yap::transform(expr, iota_terminal_transform{0}); + assert(evaluate(iota_expr) == -1); + } + + { + // Like the first expression above, this expression requires both + // overloads of iota_terminal_transform. + auto expr = boost::yap::make_terminal(sum)(-(boost::yap::make_terminal(8) + 8), 0); + assert(evaluate(expr) == -16); + + auto iota_expr = boost::yap::transform(expr, iota_terminal_transform{0}); + assert(evaluate(iota_expr) == -3); + } +} +//] -- cgit v1.2.3