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1 | /////////////////////////////////////////////////////////////////////////////// | |
2 | /// \file arg.hpp | |
3 | /// Contains definition of the argN transforms. | |
4 | // | |
5 | // Copyright 2008 Eric Niebler. Distributed under the Boost | |
6 | // Software License, Version 1.0. (See accompanying file | |
7 | // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
8 | ||
9 | #ifndef BOOST_PROTO_TRANSFORM_ARG_HPP_EAN_11_01_2007 | |
10 | #define BOOST_PROTO_TRANSFORM_ARG_HPP_EAN_11_01_2007 | |
11 | ||
12 | #include <boost/mpl/if.hpp> | |
13 | #include <boost/proto/proto_fwd.hpp> | |
14 | #include <boost/proto/traits.hpp> | |
15 | #include <boost/proto/transform/impl.hpp> | |
16 | #include <boost/type_traits/is_array.hpp> | |
17 | #include <boost/proto/transform/env.hpp> | |
18 | ||
19 | namespace boost { namespace proto | |
20 | { | |
21 | ||
22 | /// \brief A PrimitiveTransform that returns the current expression | |
23 | /// unmodified | |
24 | /// | |
25 | /// Example: | |
26 | /// | |
27 | /// \code | |
28 | /// proto::terminal<int>::type i = {42}; | |
29 | /// proto::terminal<int>::type & j = proto::_expr()(i); | |
30 | /// assert( boost::addressof(i) == boost::addressof(j) ); | |
31 | /// \endcode | |
32 | struct _expr : transform<_expr> | |
33 | { | |
34 | template<typename Expr, typename State, typename Data> | |
35 | struct impl : transform_impl<Expr, State, Data> | |
36 | { | |
37 | typedef Expr result_type; | |
38 | ||
39 | /// Returns the current expression. | |
40 | /// \param e The current expression. | |
41 | /// \return \c e | |
42 | /// \throw nothrow | |
43 | BOOST_PROTO_RETURN_TYPE_STRICT_LOOSE(result_type, typename impl::expr_param) | |
44 | operator()( | |
45 | typename impl::expr_param e | |
46 | , typename impl::state_param | |
47 | , typename impl::data_param | |
48 | ) const | |
49 | { | |
50 | return e; | |
51 | } | |
52 | }; | |
53 | }; | |
54 | ||
55 | /// \brief A PrimitiveTransform that returns the current state | |
56 | /// unmodified | |
57 | /// | |
58 | /// Example: | |
59 | /// | |
60 | /// \code | |
61 | /// proto::terminal<int>::type i = {42}; | |
62 | /// char ch = proto::_state()(i, 'a'); | |
63 | /// assert( ch == 'a' ); | |
64 | /// \endcode | |
65 | struct _state : transform<_state> | |
66 | { | |
67 | template<typename Expr, typename State, typename Data> | |
68 | struct impl : transform_impl<Expr, State, Data> | |
69 | { | |
70 | typedef State result_type; | |
71 | ||
72 | /// Returns the current state. | |
73 | /// \param s The current state. | |
74 | /// \return \c s | |
75 | /// \throw nothrow | |
76 | BOOST_PROTO_RETURN_TYPE_STRICT_LOOSE(result_type, typename impl::state_param) | |
77 | operator ()( | |
78 | typename impl::expr_param | |
79 | , typename impl::state_param s | |
80 | , typename impl::data_param | |
81 | ) const | |
82 | { | |
83 | return s; | |
84 | } | |
85 | }; | |
86 | }; | |
87 | ||
88 | /// \brief A PrimitiveTransform that returns the current data | |
89 | /// unmodified | |
90 | /// | |
91 | /// Example: | |
92 | /// | |
93 | /// \code | |
94 | /// proto::terminal<int>::type i = {42}; | |
95 | /// std::string str("hello"); | |
96 | /// std::string & data = proto::_data()(i, 'a', str); | |
97 | /// assert( &str == &data ); | |
98 | /// \endcode | |
99 | struct _data : transform<_data> | |
100 | { | |
101 | template<typename Expr, typename State, typename Data> | |
102 | struct impl | |
103 | : mpl::if_c< | |
104 | is_env<Data>::value | |
105 | , _env_var<data_type> | |
106 | , _env | |
107 | >::type::template impl<Expr, State, Data> | |
108 | {}; | |
109 | }; | |
110 | ||
111 | /// \brief A PrimitiveTransform that returns N-th child of the current | |
112 | /// expression. | |
113 | /// | |
114 | /// Example: | |
115 | /// | |
116 | /// \code | |
117 | /// proto::terminal<int>::type i = {42}; | |
118 | /// proto::terminal<int>::type & j = proto::_child_c<0>()(-i); | |
119 | /// assert( boost::addressof(i) == boost::addressof(j) ); | |
120 | /// \endcode | |
121 | template<int N> | |
122 | struct _child_c : transform<_child_c<N> > | |
123 | { | |
124 | template<typename Expr, typename State, typename Data> | |
125 | struct impl : transform_impl<Expr, State, Data> | |
126 | { | |
127 | typedef | |
128 | typename result_of::child_c<Expr, N>::type | |
129 | result_type; | |
130 | ||
131 | /// Returns the N-th child of \c e | |
132 | /// \pre <tt>arity_of\<Expr\>::value \> N</tt> | |
133 | /// \param e The current expression. | |
134 | /// \return <tt>proto::child_c\<N\>(e)</tt> | |
135 | /// \throw nothrow | |
136 | #ifdef BOOST_PROTO_STRICT_RESULT_OF | |
137 | result_type | |
138 | #else | |
139 | typename result_of::child_c<typename impl::expr_param, N>::type | |
140 | #endif | |
141 | operator ()( | |
142 | typename impl::expr_param e | |
143 | , typename impl::state_param | |
144 | , typename impl::data_param | |
145 | ) const | |
146 | { | |
147 | return proto::child_c<N>(e); | |
148 | } | |
149 | }; | |
150 | }; | |
151 | ||
152 | /// \brief A PrimitiveTransform that returns the value of the | |
153 | /// current terminal expression. | |
154 | /// | |
155 | /// Example: | |
156 | /// | |
157 | /// \code | |
158 | /// proto::terminal<int>::type i = {42}; | |
159 | /// int j = proto::_value()(i); | |
160 | /// assert( 42 == j ); | |
161 | /// \endcode | |
162 | struct _value : transform<_value> | |
163 | { | |
164 | template<typename Expr, typename State, typename Data> | |
165 | struct impl : transform_impl<Expr, State, Data> | |
166 | { | |
167 | typedef | |
168 | typename result_of::value<Expr>::type | |
169 | result_type; | |
170 | ||
171 | /// Returns the value of the specified terminal expression. | |
172 | /// \pre <tt>arity_of\<Expr\>::value == 0</tt>. | |
173 | /// \param e The current expression. | |
174 | /// \return <tt>proto::value(e)</tt> | |
175 | /// \throw nothrow | |
176 | #ifdef BOOST_PROTO_STRICT_RESULT_OF | |
177 | typename mpl::if_c<is_array<result_type>::value, result_type &, result_type>::type | |
178 | #else | |
179 | typename result_of::value<typename impl::expr_param>::type | |
180 | #endif | |
181 | operator ()( | |
182 | typename impl::expr_param e | |
183 | , typename impl::state_param | |
184 | , typename impl::data_param | |
185 | ) const | |
186 | { | |
187 | return proto::value(e); | |
188 | } | |
189 | }; | |
190 | }; | |
191 | ||
192 | /// \brief A PrimitiveTransform that does nothing | |
193 | /// and returns void. | |
194 | struct _void : transform<_void> | |
195 | { | |
196 | template<typename Expr, typename State, typename Data> | |
197 | struct impl : transform_impl<Expr, State, Data> | |
198 | { | |
199 | typedef void result_type; | |
200 | ||
201 | /// Does nothing and returns void | |
202 | void operator ()( | |
203 | typename impl::expr_param | |
204 | , typename impl::state_param | |
205 | , typename impl::data_param | |
206 | ) const | |
207 | {} | |
208 | }; | |
209 | }; | |
210 | ||
211 | /// \brief A unary CallableTransform that wraps its argument | |
212 | /// in a \c boost::reference_wrapper\<\>. | |
213 | /// | |
214 | /// Example: | |
215 | /// | |
216 | /// \code | |
217 | /// proto::terminal<int>::type i = {42}; | |
218 | /// boost::reference_wrapper<proto::terminal<int>::type> j | |
219 | /// = proto::when<_, proto::_byref(_)>()(i); | |
220 | /// assert( boost::addressof(i) == boost::addressof(j.get()) ); | |
221 | /// \endcode | |
222 | struct _byref : callable | |
223 | { | |
224 | template<typename Sig> | |
225 | struct result; | |
226 | ||
227 | template<typename This, typename T> | |
228 | struct result<This(T)> | |
229 | { | |
230 | typedef boost::reference_wrapper<T const> const type; | |
231 | }; | |
232 | ||
233 | template<typename This, typename T> | |
234 | struct result<This(T &)> | |
235 | { | |
236 | typedef boost::reference_wrapper<T> const type; | |
237 | }; | |
238 | ||
239 | /// Wrap the parameter \c t in a \c boost::reference_wrapper\<\> | |
240 | /// \param t The object to wrap | |
241 | /// \return <tt>boost::ref(t)</tt> | |
242 | /// \throw nothrow | |
243 | template<typename T> | |
244 | boost::reference_wrapper<T> const operator ()(T &t) const | |
245 | { | |
246 | return boost::reference_wrapper<T>(t); | |
247 | } | |
248 | ||
249 | /// \overload | |
250 | /// | |
251 | template<typename T> | |
252 | boost::reference_wrapper<T const> const operator ()(T const &t) const | |
253 | { | |
254 | return boost::reference_wrapper<T const>(t); | |
255 | } | |
256 | }; | |
257 | ||
258 | /// \brief A unary CallableTransform that strips references | |
259 | /// and \c boost::reference_wrapper\<\> from its argument. | |
260 | /// | |
261 | /// Example: | |
262 | /// | |
263 | /// \code | |
264 | /// proto::terminal<int>::type i = {42}; | |
265 | /// int j = 67; | |
266 | /// int k = proto::when<_, proto::_byval(proto::_state)>()(i, boost::ref(j)); | |
267 | /// assert( 67 == k ); | |
268 | /// \endcode | |
269 | struct _byval : callable | |
270 | { | |
271 | template<typename Sig> | |
272 | struct result; | |
273 | ||
274 | template<typename This, typename T> | |
275 | struct result<This(T)> | |
276 | { | |
277 | typedef T type; | |
278 | }; | |
279 | ||
280 | template<typename This, typename T> | |
281 | struct result<This(T &)> | |
282 | : result<This(T)> | |
283 | {}; | |
284 | ||
285 | template<typename This, typename T> | |
286 | struct result<This(boost::reference_wrapper<T>)> | |
287 | : result<This(T)> | |
288 | {}; | |
289 | ||
290 | /// \param t The object to unref | |
291 | /// \return <tt>t</tt> | |
292 | /// \throw nothrow | |
293 | template<typename T> | |
294 | T operator ()(T const &t) const | |
295 | { | |
296 | return t; | |
297 | } | |
298 | ||
299 | /// \overload | |
300 | /// | |
301 | template<typename T> | |
302 | T operator ()(boost::reference_wrapper<T> const &t) const | |
303 | { | |
304 | return t; | |
305 | } | |
306 | }; | |
307 | ||
308 | /// INTERNAL ONLY | |
309 | /// | |
310 | template<> | |
311 | struct is_callable<_expr> | |
312 | : mpl::true_ | |
313 | {}; | |
314 | ||
315 | /// INTERNAL ONLY | |
316 | /// | |
317 | template<> | |
318 | struct is_callable<_state> | |
319 | : mpl::true_ | |
320 | {}; | |
321 | ||
322 | /// INTERNAL ONLY | |
323 | /// | |
324 | template<> | |
325 | struct is_callable<_data> | |
326 | : mpl::true_ | |
327 | {}; | |
328 | ||
329 | /// INTERNAL ONLY | |
330 | /// | |
331 | template<int N> | |
332 | struct is_callable<_child_c<N> > | |
333 | : mpl::true_ | |
334 | {}; | |
335 | ||
336 | /// INTERNAL ONLY | |
337 | /// | |
338 | template<> | |
339 | struct is_callable<_value> | |
340 | : mpl::true_ | |
341 | {}; | |
342 | ||
343 | /// INTERNAL ONLY | |
344 | /// | |
345 | template<> | |
346 | struct is_callable<_byref> | |
347 | : mpl::true_ | |
348 | {}; | |
349 | ||
350 | /// INTERNAL ONLY | |
351 | /// | |
352 | template<> | |
353 | struct is_callable<_byval> | |
354 | : mpl::true_ | |
355 | {}; | |
356 | ||
357 | }} | |
358 | ||
359 | #endif |