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  1.  
  2. #include <cmath>
  3. #include <cstdint>
  4. #include <iomanip>
  5. #include <iostream>
  6. #include <limits>
  7.  
  8. // the upper bound must always be checked
  9. template <typename target_type, typename actual_type>
  10. bool test_upper_bound(const actual_type n)
  11. {
  12.    typedef typename std::common_type<target_type, actual_type>::type common_type;
  13.    const auto c_n = static_cast<common_type>(n);
  14.    const auto t_max = static_cast<common_type>(std::numeric_limits<target_type>::max());
  15.    return ( c_n <= t_max );
  16. }
  17.  
  18. // the lower bound is only needed to be checked explicitely in non-trivial cases, see the next to functions
  19. template <typename target_type, typename actual_type>
  20. typename std::enable_if<!(std::is_unsigned<target_type>::value), bool>::type
  21. test_lower_bound(const actual_type n)
  22. {
  23.    typedef typename std::common_type<target_type, actual_type>::type common_type;
  24.    const auto c_n = static_cast<common_type>(n);
  25.    const auto t_min = static_cast<common_type>(std::numeric_limits<target_type>::lowest());
  26.    return ( c_n >= t_min );
  27. }
  28.  
  29. // for unsigned target types, the sign of n musn't be negative
  30. // but that's not an issue with unsigned actual_type
  31. template <typename target_type, typename actual_type>
  32. typename std::enable_if<std::is_integral<target_type>::value &&
  33.                         std::is_unsigned<target_type>::value &&
  34.                         std::is_integral<actual_type>::value &&
  35.                         std::is_unsigned<actual_type>::value, bool>::type
  36. test_lower_bound(const actual_type)
  37. {
  38.    return true;
  39. }
  40.  
  41. // for unsigned target types, the sign of n musn't be negative
  42. template <typename target_type, typename actual_type>
  43. typename std::enable_if<std::is_integral<target_type>::value &&
  44.                         std::is_unsigned<target_type>::value &&
  45.                         (!std::is_integral<actual_type>::value ||
  46.                          !std::is_unsigned<actual_type>::value), bool>::type
  47. test_lower_bound(const actual_type n)
  48. {
  49.    return ( n >= 0 );
  50. }
  51.  
  52. // value may be integral if the target type is non-integral
  53. template <typename target_type, typename actual_type>
  54. typename std::enable_if<!std::is_integral<target_type>::value, bool>::type
  55. test_integrality(const actual_type)
  56. {
  57.    return true;
  58. }
  59.  
  60. // value must be integral if the target type is integral
  61. template <typename target_type, typename actual_type>
  62. typename std::enable_if<std::is_integral<target_type>::value, bool>::type
  63. test_integrality(const actual_type n)
  64. {
  65.    return ( (std::abs(n - std::floor(n)) < 1e-8) || (std::abs(n - std::ceil(n)) < 1e-8) );
  66. }
  67.  
  68. // perform check only if non-trivial
  69. template <typename target_type, typename actual_type>
  70. typename std::enable_if<!std::is_same<target_type, actual_type>::value, bool>::type
  71. CanTypeFitValue(const actual_type n)
  72. {
  73.    return test_upper_bound<target_type>(n) &&
  74.           test_lower_bound<target_type>(n) &&
  75.           test_integrality<target_type>(n);
  76. }
  77.  
  78.  
  79. // trivial case: actual_type == target_type
  80. template <typename actual_type>
  81. bool CanTypeFitValue(const actual_type)
  82. {
  83.    return true;
  84. }
  85.  
  86. int main()
  87. {
  88.    int ns[] = {6, 1203032847, 2394857, -13423, 9324, -192992929};
  89.    for ( const auto n : ns )
  90.    {
  91.       std::cout << std::setw(10) << n << "\t";
  92.       std::cout << " " << CanTypeFitValue<int8_t>(n);
  93.       std::cout << " " << CanTypeFitValue<uint8_t>(n);
  94.       std::cout << " " << CanTypeFitValue<int16_t>(n);
  95.       std::cout << " " << CanTypeFitValue<uint16_t>(n);
  96.       std::cout << " " << CanTypeFitValue<int32_t>(n);
  97.       std::cout << " " << CanTypeFitValue<uint32_t>(n);
  98.       std::cout << " " << CanTypeFitValue<int64_t>(n);
  99.       std::cout << " " << CanTypeFitValue<uint64_t>(n);
  100.       std::cout << " " << CanTypeFitValue<float>(n);
  101.       std::cout << " " << CanTypeFitValue<double>(n);
  102.       std::cout << "\n";
  103.    }
  104.    std::cout << "\n";
  105.    unsigned long long uss[] = {6, 1201146189143ull, 2397, 23};
  106.    for ( const auto n : uss )
  107.    {
  108.       std::cout << std::setw(10) << n << "\t";
  109.       std::cout << " " << CanTypeFitValue<int8_t>(n);
  110.       std::cout << " " << CanTypeFitValue<uint8_t>(n);
  111.       std::cout << " " << CanTypeFitValue<int16_t>(n);
  112.       std::cout << " " << CanTypeFitValue<uint16_t>(n);
  113.       std::cout << " " << CanTypeFitValue<int32_t>(n);
  114.       std::cout << " " << CanTypeFitValue<uint32_t>(n);
  115.       std::cout << " " << CanTypeFitValue<int64_t>(n);
  116.       std::cout << " " << CanTypeFitValue<uint64_t>(n);
  117.       std::cout << " " << CanTypeFitValue<float>(n);
  118.       std::cout << " " << CanTypeFitValue<double>(n);
  119.       std::cout << "\n";
  120.    }
  121.    std::cout << "\n";
  122.    float fs[] = {0.0, 0.5, -0.5, 1.0, -1.0, 1e10, -1e10};
  123.    for ( const auto f : fs )
  124.    {
  125.       std::cout << std::setw(10) << f << "\t";
  126.       std::cout << " " << CanTypeFitValue<int8_t>(f);
  127.       std::cout << " " << CanTypeFitValue<uint8_t>(f);
  128.       std::cout << " " << CanTypeFitValue<int16_t>(f);
  129.       std::cout << " " << CanTypeFitValue<uint16_t>(f);
  130.       std::cout << " " << CanTypeFitValue<int32_t>(f);
  131.       std::cout << " " << CanTypeFitValue<uint32_t>(f);
  132.       std::cout << " " << CanTypeFitValue<int64_t>(f);
  133.       std::cout << " " << CanTypeFitValue<uint64_t>(f);
  134.       std::cout << " " << CanTypeFitValue<float>(f);
  135.       std::cout << " " << CanTypeFitValue<double>(f);
  136.       std::cout << "\n";
  137.    }
  138. }
  139.  
Success #stdin #stdout 0s 2860KB
comments (?)
stdin 
Standard input is empty
stdout 
         6	 1 1 1 1 1 1 1 1 1 1
1203032847	 0 0 0 0 1 1 1 1 1 1
   2394857	 0 0 0 0 1 1 1 1 1 1
    -13423	 0 0 1 0 1 0 1 0 1 1
      9324	 0 0 1 1 1 1 1 1 1 1
-192992929	 0 0 0 0 1 0 1 0 1 1

         6	 0 1 0 1 0 1 0 1 1 1
1201146189143	 0 0 0 0 0 0 0 1 1 1
      2397	 0 0 0 1 0 1 0 1 1 1
        23	 0 1 0 1 0 1 0 1 1 1

         0	 1 1 1 1 1 1 1 1 1 1
       0.5	 0 0 0 0 0 0 0 0 1 1
      -0.5	 0 0 0 0 0 0 0 0 1 1
         1	 1 1 1 1 1 1 1 1 1 1
        -1	 1 0 1 0 1 0 1 0 1 1
     1e+10	 0 0 0 0 0 0 1 1 1 1
    -1e+10	 0 0 0 0 0 0 1 0 1 1
https://ideone.com/lBxnAW
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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