std::numeric_limits<T>::denorm_min (3) - Linux Manuals

std::numeric_limits<T>::denorm_min: std::numeric_limits<T>::denorm_min

NAME

std::numeric_limits<T>::denorm_min - std::numeric_limits<T>::denorm_min

Synopsis

static T denorm_min() throw(); (until C++11)
static constexpr T denorm_min() noexcept; (since C++11)

Returns the minimum positive subnormal_value of the type T, if std::numeric_limits<T>::has_denorm != std::denorm_absent, otherwise returns std::numeric_limits<T>::min(). Only meaningful for floating-point types.

Return value

T std::numeric_limits<T>::denorm_min()
/* non-specialized */ T()
bool false
char 0
signed char 0
unsigned char 0
wchar_t 0
char8_t 0
char16_t 0
char32_t 0
short 0
unsigned short 0
int 0
unsigned int 0
long 0
unsigned long 0
long long 0
unsigned long long 0
float 2-149
                      if std::numeric_limits<float>::is_iec559 == true
double 2-1074
                      if std::numeric_limits<double>::is_iec559 == true
long double /* implementation-defined */

Example

Demonstates the underlying bit structure of the denorm_min() and prints the values
// Run this code

  #include <cassert>
  #include <cstdint>
  #include <cstring>
  #include <iostream>
  #include <limits>

  int main()
  {
      // the smallest subnormal value has sign bit = 0, exponent = 0
      // and only the least significant bit of the fraction is 1
      std::uint32_t denorm_bits = 0x0001;
      float denorm_float;
      std::memcpy(&denorm_float, &denorm_bits, sizeof(float));

      assert(denorm_float == std::numeric_limits<float>::denorm_min());

      std::cout << "float\tmin()\t\tdenorm_min()\n";
      std::cout << "\t" << std::numeric_limits<float>::min() << '\t';
      std::cout << std::numeric_limits<float>::denorm_min() << '\n';

      std::cout << "double\tmin()\t\tdenorm_min()\n";
      std::cout << "\t" << std::numeric_limits<double>::min() << '\t';
      std::cout << std::numeric_limits<double>::denorm_min() << '\n';
  }

Possible output:

  float min() denorm_min()

   1.17549e-38 1.4013e-45

  double min() denorm_min()

   2.22507e-308 4.94066e-324