NAME¶

std::numeric_limits::denorm_min - std::numeric_limits::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() for floating point types and T() for all other types.
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 (since C++20) 0
char16_t (since C++11) 0
char32_t (since C++11) 0
short 0
unsigned short 0
int 0
unsigned int 0
long 0
unsigned long 0
long long (since C++11) 0
unsigned long long since (since 0
C++11)
FLT_TRUE_MIN (\(\scriptsize 2^{-149}\)2-149
float if
std::numeric_limits<float>::is_iec559 is true)
DBL_TRUE_MIN (\(\scriptsize 2^{-1074}\)2-1074
double if
std::numeric_limits<double>::is_iec559 is true)
long double LDBL_TRUE_MIN

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

See also¶

min returns the smallest finite value of the given type
[static] (public static member function)
has_denorm identifies the denormalization style used by the floating-point
[static] type
(public static member constant)
lowest returns the lowest finite value of the given type
[static] (C++11) (public static member function)