1///////////////////////////////////////////////////////////////////////////////
2// calculator.hpp
3//
4// Copyright 2008 Eric Niebler. Distributed under the Boost
5// Software License, Version 1.0. (See accompanying file
6// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7
8#include <boost/proto/core.hpp>
9#include <boost/proto/context.hpp>
10#include <boost/test/unit_test.hpp>
11
12using namespace boost;
13
14struct placeholder {};
15proto::terminal<placeholder>::type const _1 = {.child0: {}};
16
17struct calculator : proto::callable_context<calculator const>
18{
19 typedef int result_type;
20
21 calculator(int i)
22 : i_(i)
23 {}
24
25 int operator ()(proto::tag::terminal, placeholder) const
26 {
27 return this->i_;
28 }
29
30 int operator ()(proto::tag::terminal, int j) const
31 {
32 return j;
33 }
34
35 template<typename Left, typename Right>
36 int operator ()(proto::tag::plus, Left const &left, Right const &right) const
37 {
38 return proto::eval(left, *this) + proto::eval(right, *this);
39 }
40
41 template<typename Left, typename Right>
42 int operator ()(proto::tag::minus, Left const &left, Right const &right) const
43 {
44 return proto::eval(left, *this) - proto::eval(right, *this);
45 }
46
47 template<typename Left, typename Right>
48 int operator ()(proto::tag::multiplies, Left const &left, Right const &right) const
49 {
50 return proto::eval(left, *this) * proto::eval(right, *this);
51 }
52
53 template<typename Left, typename Right>
54 int operator ()(proto::tag::divides, Left const &left, Right const &right) const
55 {
56 return proto::eval(left, *this) / proto::eval(right, *this);
57 }
58
59private:
60 int i_;
61};
62
63template<typename Fun, typename Expr>
64struct functional
65{
66 typedef typename proto::result_of::eval<Expr, Fun>::type result_type;
67
68 functional(Expr const &expr)
69 : expr_(expr)
70 {}
71
72 template<typename T>
73 result_type operator ()(T const &t) const
74 {
75 Fun fun(t);
76 return proto::eval(this->expr_, fun);
77 }
78
79private:
80 Expr const &expr_;
81};
82
83template<typename Fun, typename Expr>
84functional<Fun, Expr> as(Expr const &expr)
85{
86 return functional<Fun, Expr>(expr);
87}
88
89void test_calculator()
90{
91 BOOST_CHECK_EQUAL(10, proto::eval(((_1 + 42)-3)/4, calculator(1)));
92 BOOST_CHECK_EQUAL(11, proto::eval(((_1 + 42)-3)/4, calculator(5)));
93
94 BOOST_CHECK_EQUAL(10, as<calculator>(((_1 + 42)-3)/4)(1));
95 BOOST_CHECK_EQUAL(11, as<calculator>(((_1 + 42)-3)/4)(5));
96}
97
98using namespace unit_test;
99///////////////////////////////////////////////////////////////////////////////
100// init_unit_test_suite
101//
102test_suite* init_unit_test_suite( int argc, char* argv[] )
103{
104 test_suite *test = BOOST_TEST_SUITE("test immediate evaluation of proto parse trees");
105
106 test->add(BOOST_TEST_CASE(&test_calculator));
107
108 return test;
109}
110

source code of boost/libs/proto/test/calculator.cpp