1 files changed, 134 insertions, 0 deletions
diff --git a/src/boost/libs/variant/test/test3.cpp b/src/boost/libs/variant/test/test3.cpp
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+++ b/src/boost/libs/variant/test/test3.cpp
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+//-----------------------------------------------------------------------------
+// boost-libs variant/test/test3.cpp source file
+// See http://www.boost.org for updates, documentation, and revision history.
+//-----------------------------------------------------------------------------
+//
+// Copyright (c) 2003
+// Eric Friedman, Itay Maman
+//
+// 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/core/lightweight_test.hpp"
+#include "boost/variant.hpp"
+
+#include <iostream>
+#include <sstream>
+#include <string>
+
+/////////////////////////////////////////////////////////////////////
+
+using boost::variant;
+using boost::recursive_wrapper;
+using std::cout;
+using std::endl;
+
+/////////////////////////////////////////////////////////////////////
+/////////////////////////////////////////////////////////////////////
+
+struct Add;
+struct Sub;
+
+typedef variant<int, recursive_wrapper<Add>, recursive_wrapper<Sub> > Expr;
+
+struct Sub
+{
+   Sub();
+   Sub(const Expr& l, const Expr& r);
+   Sub(const Sub& other);
+
+   Expr lhs_;
+   Expr rhs_;
+};
+
+struct Add
+{
+   Add() { }
+   Add(const Expr& l, const Expr& r) : lhs_(l), rhs_(r) { }
+   Add(const Add& other) : lhs_(other.lhs_), rhs_(other.rhs_) { }
+
+   Expr lhs_;
+   Expr rhs_;
+};
+
+Sub::Sub() { }
+Sub::Sub(const Expr& l, const Expr& r) : lhs_(l), rhs_(r) { }
+Sub::Sub(const Sub& other) : lhs_(other.lhs_), rhs_(other.rhs_) { }
+
+
+//
+// insert-to operators
+//
+std::ostream& operator<<(std::ostream& out, const Sub& a);
+
+std::ostream& operator<<(std::ostream& out, const Add& a)
+{
+   out << '(' << a.lhs_ << '+' << a.rhs_ << ')';
+   return out;
+}
+
+std::ostream& operator<<(std::ostream& out, const Sub& a)
+{
+   out << '(' << a.lhs_ << '-' << a.rhs_ << ')';
+   return out;
+}
+
+//
+// Expression evaluation visitor
+//
+struct Calculator : boost::static_visitor<int>
+{
+   Calculator()  { }
+
+   int operator()(Add& x) const
+   {
+      Calculator calc;
+      int n1 = boost::apply_visitor(calc, x.lhs_);
+      int n2 = boost::apply_visitor(calc, x.rhs_);
+      
+      return n1 + n2;
+   }
+
+   int operator()(Sub& x) const
+   {
+      return boost::apply_visitor(Calculator(), x.lhs_) 
+         - boost::apply_visitor(Calculator(), x.rhs_);
+   }
+
+   int operator()(Expr& x) const
+   {
+      Calculator calc;
+      return boost::apply_visitor(calc, x);
+   }
+
+   int operator()(int x) const
+   {
+      return x;
+   }
+
+}; // Calculator
+
+
+/////////////////////////////////////////////////////////////////////
+
+
+int main()
+{
+
+   int n = 13;
+   Expr e1( Add(n, Sub(Add(40,2),Add(10,4))) ); //n + (40+2)-(10+14) = n+28
+
+   std::ostringstream e1_str;
+   e1_str << e1;
+
+   BOOST_TEST(e1.type() == boost::typeindex::type_id<Add>());
+   BOOST_TEST(e1_str.str() == "(13+((40+2)-(10+4)))");
+
+   //Evaluate expression
+   int res = boost::apply_visitor(Calculator(), e1);
+   BOOST_TEST(res == n + 28);
+
+   return boost::report_errors();
+}
+