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  1. #include <tuple>
  2. #include <utility>
  3.  
  4. #include <boost/preprocessor.hpp>
  5.  
  6. #define FOREACH_PREFIX BOOST_PP_CAT(__foreach_, __LINE__)
  7.  
  8. #define FOREACH_BODY     BOOST_PP_CAT(FOREACH_PREFIX, _body__)
  9. #define FOREACH_BREAK    BOOST_PP_CAT(FOREACH_PREFIX, _break__)
  10. #define FOREACH_CONTINUE BOOST_PP_CAT(FOREACH_PREFIX, _continue__)
  11. #define FOREACH_ELEM     BOOST_PP_CAT(FOREACH_PREFIX, _elem__)
  12. #define FOREACH_ONCE     BOOST_PP_CAT(FOREACH_PREFIX, _once__)
  13.  
  14. #define foreachpair(KEY, VALUE, ELEMS)                                     \
  15.   for (auto&& FOREACH_ELEM : ELEMS)                                        \
  16.     if (false) FOREACH_BREAK: break; /* set up the break path */           \
  17.     else if (bool FOREACH_CONTINUE = false) {} /* var decl */              \
  18.     else if (true) goto FOREACH_BODY; /* skip the loop exit checks */      \
  19.     else for (;;) /* determine whether we should break or continue. */     \
  20.       if (!FOREACH_CONTINUE) goto FOREACH_BREAK; /* break */               \
  21.       else if (true) break; /* continue */                                 \
  22.       else                                                                 \
  23.         FOREACH_BODY:                                                      \
  24.         if (bool FOREACH_ONCE = false) {} /* var decl */                   \
  25.         else for (KEY = std::get<0>(                                       \
  26.                       std::forward<decltype(FOREACH_ELEM)>(FOREACH_ELEM)); \
  27.                   !FOREACH_ONCE;                                           \
  28.                   FOREACH_ONCE = true)                                     \
  29.           for (VALUE = std::get<1>(                                        \
  30.                    std::forward<decltype(FOREACH_ELEM)>(FOREACH_ELEM));    \
  31.                !FOREACH_CONTINUE;                                          \
  32.                FOREACH_CONTINUE = true)
  33.  
  34. /* -------------------------------------------------------------------------- */
  35.  
  36. #include <iostream>
  37. #include <map>
  38. #include <vector>
  39.  
  40. int main() {
  41.   {
  42.   	std::cout << "{}: start" << std::endl;
  43.     std::map<int, double> elems;
  44.     foreachpair (int key, double value, elems) {
  45.       std::cout << key << " " << value << std::endl;
  46.     }
  47.     std::cout << "{}: end" << std::endl;
  48.   }
  49.   {
  50.   	std::cout << "{{101, 202}, {303, 404}}: start" << std::endl;
  51.     std::map<int, int> elems = {{101, 202}, {303, 404}};
  52.     foreachpair (int key, int value, elems) {
  53.       std::cout << key << " " << value << std::endl;
  54.     }
  55.     std::cout << "{{101, 202}, {303, 404}}: end" << std::endl;
  56.   }
  57.   {
  58.   	std::cout << "break: {{1, 2}, {3, 4}}: start" << std::endl;
  59.     std::map<int, int> elems = {{1, 2}, {3, 4}};
  60.     foreachpair (int key, int value, elems) {
  61.       std::cout << key << " " << value << std::endl;
  62.       if (key == 1) break;
  63.     }
  64.     std::cout << "break: {{1, 2}, {3, 4}}: end" << std::endl;
  65.   }
  66.   {
  67.   	std::cout << "continue: {{1, 2}, {3, 4}}: start" << std::endl;
  68.     std::map<int, int> elems = {{1, 2}, {3, 4}};
  69.     foreachpair (int key, int value, elems) {
  70.       if (key == 1) continue;
  71.       std::cout << key << " " << value << std::endl;
  72.     }
  73.     std::cout << "continue: {{1, 2}, {3, 4}}: end" << std::endl;
  74.   }
  75.   {
  76.   	std::cout << "{{1, 2}, {3, 4}}: start" << std::endl;
  77.     std::vector<std::tuple<int, int>> elems = {std::make_tuple(1, 2),
  78.                                                std::make_tuple(3, 4)};
  79.     foreachpair (int key, int value, elems) {
  80.       std::cout << key << " " << value << std::endl;
  81.     }
  82.     std::cout << "{{1, 2}, {3, 4}}: end" << std::endl;
  83.   }
  84. }
Success #stdin #stdout 0s 3464KB
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stdin
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Standard input is empty
stdout
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{}: start
{}: end
{{101, 202}, {303, 404}}: start
101 202
303 404
{{101, 202}, {303, 404}}: end
break: {{1, 2}, {3, 4}}: start
1 2
break: {{1, 2}, {3, 4}}: end
continue: {{1, 2}, {3, 4}}: start
3 4
continue: {{1, 2}, {3, 4}}: end
{{1, 2}, {3, 4}}: start
1 2
3 4
{{1, 2}, {3, 4}}: end
https://ideone.com/BHcAz8
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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