1 | // bind_tests_advanced.cpp -- The Boost Lambda Library ------------------ |
2 | // |
3 | // Copyright (C) 2000-2003 Jaakko Jarvi (jaakko.jarvi@cs.utu.fi) |
4 | // Copyright (C) 2000-2003 Gary Powell (powellg@amazon.com) |
5 | // Copyright (C) 2010 Steven Watanabe |
6 | // |
7 | // Distributed under the Boost Software License, Version 1.0. (See |
8 | // accompanying file LICENSE_1_0.txt or copy at |
9 | // http://www.boost.org/LICENSE_1_0.txt) |
10 | // |
11 | // For more information, see www.boost.org |
12 | |
13 | // ----------------------------------------------------------------------- |
14 | |
15 | |
16 | #include <boost/core/lightweight_test.hpp> |
17 | #define BOOST_CHECK BOOST_TEST |
18 | |
19 | #include "boost/lambda/lambda.hpp" |
20 | #include "boost/lambda/bind.hpp" |
21 | |
22 | |
23 | #include "boost/any.hpp" |
24 | #include "boost/type_traits/is_reference.hpp" |
25 | #include "boost/mpl/assert.hpp" |
26 | #include "boost/mpl/if.hpp" |
27 | |
28 | #include <iostream> |
29 | |
30 | #include <functional> |
31 | |
32 | #include <algorithm> |
33 | |
34 | |
35 | using namespace boost::lambda; |
36 | namespace bl = boost::lambda; |
37 | |
38 | int sum_0() { return 0; } |
39 | int sum_1(int a) { return a; } |
40 | int sum_2(int a, int b) { return a+b; } |
41 | |
42 | int product_2(int a, int b) { return a*b; } |
43 | |
44 | // unary function that returns a pointer to a binary function |
45 | typedef int (*fptr_type)(int, int); |
46 | fptr_type sum_or_product(bool x) { |
47 | return x ? sum_2 : product_2; |
48 | } |
49 | |
50 | // a nullary functor that returns a pointer to a unary function that |
51 | // returns a pointer to a binary function. |
52 | struct which_one { |
53 | typedef fptr_type (*result_type)(bool x); |
54 | template <class T> struct sig { typedef result_type type; }; |
55 | |
56 | result_type operator()() const { return sum_or_product; } |
57 | }; |
58 | |
59 | void test_nested_binds() |
60 | { |
61 | int j = 2; int k = 3; |
62 | |
63 | // bind calls can be nested (the target function can be a lambda functor) |
64 | // The interpretation is, that the innermost lambda functor returns something |
65 | // that is bindable (another lambda functor, function pointer ...) |
66 | bool condition; |
67 | |
68 | condition = true; |
69 | BOOST_CHECK(bind(bind(&sum_or_product, _1), 1, 2)(condition)==3); |
70 | BOOST_CHECK(bind(bind(&sum_or_product, _1), _2, _3)(condition, j, k)==5); |
71 | |
72 | condition = false; |
73 | BOOST_CHECK(bind(bind(&sum_or_product, _1), 1, 2)(condition)==2); |
74 | BOOST_CHECK(bind(bind(&sum_or_product, _1), _2, _3)(condition, j, k)==6); |
75 | |
76 | |
77 | which_one wo; |
78 | BOOST_CHECK(bind(bind(bind(wo), _1), _2, _3)(condition, j, k)==6); |
79 | |
80 | |
81 | return; |
82 | } |
83 | |
84 | |
85 | // unlambda ------------------------------------------------- |
86 | |
87 | // Sometimes it may be necessary to prevent the argument substitution of |
88 | // taking place. For example, we may end up with a nested bind expression |
89 | // inadvertently when using the target function is received as a parameter |
90 | |
91 | template<class F> |
92 | int call_with_100(const F& f) { |
93 | |
94 | |
95 | |
96 | // bind(f, _1)(make_const(100)); |
97 | // This would result in; |
98 | // bind(_1 + 1, _1)(make_const(100)) , which would be a compile time error |
99 | |
100 | return bl::bind(unlambda(f), _1)(make_const(t: 100)); |
101 | |
102 | // for other functors than lambda functors, unlambda has no effect |
103 | // (except for making them const) |
104 | } |
105 | |
106 | template<class F> |
107 | int call_with_101(const F& f) { |
108 | |
109 | return bind(unlambda(f), _1)(make_const(t: 101)); |
110 | |
111 | } |
112 | |
113 | |
114 | void test_unlambda() { |
115 | |
116 | int i = 1; |
117 | |
118 | BOOST_CHECK(unlambda(_1 + _2)(i, i) == 2); |
119 | BOOST_CHECK(unlambda(++var(i))() == 2); |
120 | BOOST_CHECK(call_with_100(_1 + 1) == 101); |
121 | |
122 | |
123 | BOOST_CHECK(call_with_101(_1 + 1) == 102); |
124 | |
125 | #if defined(BOOST_NO_CXX11_HDR_FUNCTIONAL) |
126 | |
127 | BOOST_CHECK(call_with_100(bl::bind(std_functor(std::bind1st(std::plus<int>(), 1)), _1)) == 101); |
128 | |
129 | #elif BOOST_CXX_VERSION > 201703L |
130 | |
131 | // In C++20, standard functors no longer have ::result_type |
132 | BOOST_CHECK(call_with_100(bl::bind(std::bind(std::plus<int>(), 1, std::placeholders::_1), _1)) == 101); |
133 | |
134 | #elif defined(BOOST_MSVC) && BOOST_MSVC < 1900 |
135 | |
136 | // Mysterious failures under msvc-12.0 and below |
137 | |
138 | #else |
139 | |
140 | BOOST_CHECK(call_with_100(bl::bind(std_functor(std::bind(std::plus<int>(), 1, std::placeholders::_1)), _1)) == 101); |
141 | |
142 | #endif |
143 | |
144 | #if BOOST_CXX_VERSION <= 201703L |
145 | |
146 | // std_functor insturcts LL that the functor defines a result_type typedef |
147 | // rather than a sig template. |
148 | bl::bind(a1: std_functor(f: std::plus<int>()), a2: _1, a3: _2)(i, i); |
149 | |
150 | #else |
151 | |
152 | // In C++20, standard functors no longer have ::result_type |
153 | bl::bind(std::plus<int>(), _1, _2)(i, i); |
154 | |
155 | #endif |
156 | } |
157 | |
158 | |
159 | |
160 | |
161 | // protect ------------------------------------------------------------ |
162 | |
163 | // protect protects a lambda functor from argument substitution. |
164 | // protect is useful e.g. with nested stl algorithm calls. |
165 | |
166 | namespace ll { |
167 | |
168 | struct for_each { |
169 | |
170 | // note, std::for_each returns it's last argument |
171 | // We want the same behaviour from our ll::for_each. |
172 | // However, the functor can be called with any arguments, and |
173 | // the return type thus depends on the argument types. |
174 | |
175 | // 1. Provide a sig class member template: |
176 | |
177 | // The return type deduction system instantiate this class as: |
178 | // sig<Args>::type, where Args is a boost::tuples::cons-list |
179 | // The head type is the function object type itself |
180 | // cv-qualified (so it is possilbe to provide different return types |
181 | // for differently cv-qualified operator()'s. |
182 | |
183 | // The tail type is the list of the types of the actual arguments the |
184 | // function was called with. |
185 | // So sig should contain a typedef type, which defines a mapping from |
186 | // the operator() arguments to its return type. |
187 | // Note, that it is possible to provide different sigs for the same functor |
188 | // if the functor has several operator()'s, even if they have different |
189 | // number of arguments. |
190 | |
191 | // Note, that the argument types in Args are guaranteed to be non-reference |
192 | // types, but they can have cv-qualifiers. |
193 | |
194 | template <class Args> |
195 | struct sig { |
196 | typedef typename boost::remove_const< |
197 | typename boost::tuples::element<3, Args>::type |
198 | >::type type; |
199 | }; |
200 | |
201 | template <class A, class B, class C> |
202 | C |
203 | operator()(const A& a, const B& b, const C& c) const |
204 | { return std::for_each(a, b, c);} |
205 | }; |
206 | |
207 | } // end of ll namespace |
208 | |
209 | void test_protect() |
210 | { |
211 | int i = 0; |
212 | int b[3][5]; |
213 | int* a[3]; |
214 | |
215 | for(int j=0; j<3; ++j) a[j] = b[j]; |
216 | |
217 | std::for_each(first: a, last: a+3, |
218 | f: bind(a1: ll::for_each(), a2: _1, a3: _1 + 5, a4: protect(a1: _1 = ++var(t&: i)))); |
219 | |
220 | // This is how you could output the values (it is uncommented, no output |
221 | // from a regression test file): |
222 | // std::for_each(a, a+3, |
223 | // bind(ll::for_each(), _1, _1 + 5, |
224 | // std::cout << constant("\nLine ") << (&_1 - a) << " : " |
225 | // << protect(_1) |
226 | // ) |
227 | // ); |
228 | |
229 | int sum = 0; |
230 | |
231 | std::for_each(first: a, last: a+3, |
232 | f: bind(a1: ll::for_each(), a2: _1, a3: _1 + 5, |
233 | a4: protect(a1: sum += _1)) |
234 | ); |
235 | BOOST_CHECK(sum == (1+15)*15/2); |
236 | |
237 | sum = 0; |
238 | |
239 | std::for_each(first: a, last: a+3, |
240 | f: bind(a1: ll::for_each(), a2: _1, a3: _1 + 5, |
241 | a4: sum += 1 + protect(a1: _1)) // add element count |
242 | ); |
243 | BOOST_CHECK(sum == (1+15)*15/2 + 15); |
244 | |
245 | (1 + protect(a1: _1))(sum); |
246 | |
247 | int k = 0; |
248 | ((k += constant(t: 1)) += protect(a1: constant(t: 2)))(); |
249 | BOOST_CHECK(k==1); |
250 | |
251 | k = 0; |
252 | ((k += constant(t: 1)) += protect(a1: constant(t: 2)))()(); |
253 | BOOST_CHECK(k==3); |
254 | |
255 | // note, the following doesn't work: |
256 | |
257 | // ((var(k) = constant(1)) = protect(constant(2)))(); |
258 | |
259 | // (var(k) = constant(1))() returns int& and thus the |
260 | // second assignment fails. |
261 | |
262 | // We should have something like: |
263 | // bind(var, var(k) = constant(1)) = protect(constant(2)))(); |
264 | // But currently var is not bindable. |
265 | |
266 | // The same goes with ret. A bindable ret could be handy sometimes as well |
267 | // (protect(std::cout << _1), std::cout << _1)(i)(j); does not work |
268 | // because the comma operator tries to store the result of the evaluation |
269 | // of std::cout << _1 as a copy (and you can't copy std::ostream). |
270 | // something like this: |
271 | // (protect(std::cout << _1), bind(ref, std::cout << _1))(i)(j); |
272 | |
273 | |
274 | // the stuff below works, but we do not want extra output to |
275 | // cout, must be changed to stringstreams but stringstreams do not |
276 | // work due to a bug in the type deduction. Will be fixed... |
277 | #if 0 |
278 | // But for now, ref is not bindable. There are other ways around this: |
279 | |
280 | int x = 1, y = 2; |
281 | (protect(std::cout << _1), (std::cout << _1, 0))(x)(y); |
282 | |
283 | // added one dummy value to make the argument to comma an int |
284 | // instead of ostream& |
285 | |
286 | // Note, the same problem is more apparent without protect |
287 | // (std::cout << 1, std::cout << constant(2))(); // does not work |
288 | |
289 | (boost::ref(std::cout << 1), std::cout << constant(2))(); // this does |
290 | |
291 | #endif |
292 | |
293 | } |
294 | |
295 | |
296 | void test_lambda_functors_as_arguments_to_lambda_functors() { |
297 | |
298 | // lambda functor is a function object, and can therefore be used |
299 | // as an argument to another lambda functors function call object. |
300 | |
301 | // Note however, that the argument/type substitution is not entered again. |
302 | // This means, that something like this will not work: |
303 | |
304 | (_1 + _2)(_1, make_const(t: 7)); |
305 | (_1 + _2)(bind(a1: &sum_0), make_const(t: 7)); |
306 | |
307 | // or it does work, but the effect is not to call |
308 | // sum_0() + 7, but rather |
309 | // bind(sum_0) + 7, which results in another lambda functor |
310 | // (lambda functor + int) and can be called again |
311 | BOOST_CHECK((_1 + _2)(bind(&sum_0), make_const(7))() == 7); |
312 | |
313 | int i = 3, j = 12; |
314 | BOOST_CHECK((_1 - _2)(_2, _1)(i, j) == j - i); |
315 | |
316 | // also, note that lambda functor are no special case for bind if received |
317 | // as a parameter. In oder to be bindable, the functor must |
318 | // defint the sig template, or then |
319 | // the return type must be defined within the bind call. Lambda functors |
320 | // do define the sig template, so if the return type deduction system |
321 | // covers the case, there is no need to specify the return type |
322 | // explicitly. |
323 | |
324 | int a = 5, b = 6; |
325 | |
326 | // Let type deduction find out the return type |
327 | BOOST_CHECK(bind(_1, _2, _3)(unlambda(_1 + _2), a, b) == 11); |
328 | |
329 | //specify it yourself: |
330 | BOOST_CHECK(bind(_1, _2, _3)(ret<int>(_1 + _2), a, b) == 11); |
331 | BOOST_CHECK(ret<int>(bind(_1, _2, _3))(_1 + _2, a, b) == 11); |
332 | BOOST_CHECK(bind<int>(_1, _2, _3)(_1 + _2, a, b) == 11); |
333 | |
334 | bind(a1: _1,a2: 1.0)(_1+_1); |
335 | return; |
336 | |
337 | } |
338 | |
339 | |
340 | void test_const_parameters() { |
341 | |
342 | // (_1 + _2)(1, 2); // this would fail, |
343 | |
344 | // Either make arguments const: |
345 | BOOST_CHECK((_1 + _2)(make_const(1), make_const(2)) == 3); |
346 | |
347 | // Or use const_parameters: |
348 | BOOST_CHECK(const_parameters(_1 + _2)(1, 2) == 3); |
349 | |
350 | |
351 | |
352 | } |
353 | |
354 | void test_rvalue_arguments() |
355 | { |
356 | // Not quite working yet. |
357 | // Problems with visual 7.1 |
358 | // BOOST_CHECK((_1 + _2)(1, 2) == 3); |
359 | } |
360 | |
361 | void test_break_const() |
362 | { |
363 | |
364 | // break_const is currently unnecessary, as LL supports perfect forwarding |
365 | // for up to there argument lambda functors, and LL does not support |
366 | // lambda functors with more than 3 args. |
367 | |
368 | // I'll keep the test case around anyway, if more arguments will be supported |
369 | // in the future. |
370 | |
371 | |
372 | |
373 | // break_const breaks constness! Be careful! |
374 | // You need this only if you need to have side effects on some argument(s) |
375 | // and some arguments are non-const rvalues and your lambda functors |
376 | // take more than 3 arguments. |
377 | |
378 | |
379 | int i = 1; |
380 | // OLD COMMENT: (_1 += _2)(i, 2) // fails, 2 is a non-const rvalue |
381 | // OLD COMMENT: const_parameters(_1 += _2)(i, 2) // fails, side-effect to i |
382 | break_const(lf: _1 += _2)(i, 2); // ok |
383 | BOOST_CHECK(i == 3); |
384 | } |
385 | |
386 | template<class T> |
387 | struct func { |
388 | template<class Args> |
389 | struct sig { |
390 | typedef typename boost::tuples::element<1, Args>::type arg1; |
391 | // If the argument type is not the same as the expected type, |
392 | // return void, which will cause an error. Note that we |
393 | // can't just assert that the types are the same, because |
394 | // both const and non-const versions can be instantiated |
395 | // even though only one is ultimately used. |
396 | typedef typename boost::mpl::if_<boost::is_same<arg1, T>, |
397 | typename boost::remove_const<arg1>::type, |
398 | void |
399 | >::type type; |
400 | }; |
401 | template<class U> |
402 | U operator()(const U& arg) const { |
403 | return arg; |
404 | } |
405 | }; |
406 | |
407 | void test_sig() |
408 | { |
409 | int i = 1; |
410 | BOOST_CHECK(bind(func<int>(), 1)() == 1); |
411 | BOOST_CHECK(bind(func<const int>(), _1)(static_cast<const int&>(i)) == 1); |
412 | BOOST_CHECK(bind(func<int>(), _1)(i) == 1); |
413 | } |
414 | |
415 | class base { |
416 | public: |
417 | virtual int foo() = 0; |
418 | }; |
419 | |
420 | class derived : public base { |
421 | public: |
422 | virtual int foo() { |
423 | return 1; |
424 | } |
425 | }; |
426 | |
427 | void test_abstract() |
428 | { |
429 | derived d; |
430 | base& b = d; |
431 | BOOST_CHECK(bind(&base::foo, var(b))() == 1); |
432 | BOOST_CHECK(bind(&base::foo, *_1)(&b) == 1); |
433 | } |
434 | |
435 | int main() { |
436 | |
437 | test_nested_binds(); |
438 | test_unlambda(); |
439 | test_protect(); |
440 | test_lambda_functors_as_arguments_to_lambda_functors(); |
441 | test_const_parameters(); |
442 | test_rvalue_arguments(); |
443 | test_break_const(); |
444 | test_sig(); |
445 | test_abstract(); |
446 | return boost::report_errors(); |
447 | } |
448 | |