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  1. #include <iomanip>
  2. #include <ios>
  3. #include <iostream>
  4. #include <type_traits>
  5.  
  6. using namespace std;
  7.  
  8. #define NEW_SECTION(title) cout << endl\
  9. 	<< "-------- " << #title << " --------" << endl << endl;
  10.  
  11. #define IS_SAME(...) cout << setw(43)\
  12. 	<< ("is_same<" + string(#__VA_ARGS__) + ">::value")\
  13. 	<< " == " << boolalpha << is_same<__VA_ARGS__>::value << endl
  14.  
  15. typedef char char_t; // Char type
  16. typedef char* char_ptr; // Char pointer
  17. typedef const char* char_const_ptr; // Char const pointer
  18.  
  19. int main() {
  20. 	IS_SAME( char, char );					// Obviously true
  21. 	IS_SAME( char, float );					// Obviously false
  22.  
  23. 	NEW_SECTION(char_t);
  24. 	IS_SAME( char, char_t );				// true: OK
  25. 	IS_SAME( const char, char_t );			// false: OK
  26. 	IS_SAME( char, const char_t );			// false: OK
  27. 	IS_SAME( const char, const char_t );	// true: OK
  28.  
  29. 	NEW_SECTION(char_ptr);
  30. 	IS_SAME( char*, char_ptr );				// true: OK
  31. 	IS_SAME( const char*, char_ptr );		// false: OK
  32. 	IS_SAME( char*, const char_ptr );		// false: OK
  33. 	IS_SAME( const char*, const char_ptr );	// false: Why?
  34. 	IS_SAME( char* const, char_ptr );		// false: OK
  35. 	IS_SAME( char* const, const char_ptr );	// true: Why?
  36.  
  37. 	NEW_SECTION(char_const_ptr);
  38. 	IS_SAME( char*, char_const_ptr );		// false: OK
  39. 	IS_SAME( const char*, char_const_ptr );	// true: OK
  40. 	IS_SAME( char* const, char_const_ptr );	// false: OK
  41. 	return 0;
  42. }
  43.  
Success #stdin #stdout 0.01s 5440KB
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stdin
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Standard input is empty
stdout
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                 is_same<char, char>::value == true
                is_same<char, float>::value == false

-------- char_t --------

               is_same<char, char_t>::value == true
         is_same<const char, char_t>::value == false
         is_same<char, const char_t>::value == false
   is_same<const char, const char_t>::value == true

-------- char_ptr --------

            is_same<char*, char_ptr>::value == true
      is_same<const char*, char_ptr>::value == false
      is_same<char*, const char_ptr>::value == false
is_same<const char*, const char_ptr>::value == false
      is_same<char* const, char_ptr>::value == false
is_same<char* const, const char_ptr>::value == true

-------- char_const_ptr --------

      is_same<char*, char_const_ptr>::value == false
is_same<const char*, char_const_ptr>::value == true
is_same<char* const, char_const_ptr>::value == false
https://ideone.com/Rk9gD9
language:
C++14 (gcc 8.3)
created:
2 years ago
visibility:
secret

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