std::numeric_limits<T>::denorm_min
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 |
| signedchar |
0 |
| unsignedchar |
0 |
| wchar_t |
0 |
| char8_t (since C++20) |
0 |
| char16_t (since C++11) |
0 |
| char32_t (since C++11) |
0 |
| short |
0 |
| unsignedshort |
0 |
| int |
0 |
| unsignedint |
0 |
| long |
0 |
| unsignedlong |
0 |
| longlong (since C++11) |
0 |
| unsignedlonglong since (since C++11) |
0 |
| float |
FLT_TRUE_MIN (\(\scriptsize 2^{-149}\)2-149 ifstd::numeric_limits<float>::is_iec559 is true) |
| double |
DBL_TRUE_MIN (\(\scriptsize 2^{-1074}\)2-1074 ifstd::numeric_limits<double>::is_iec559 is true) |
| longdouble |
LDBL_TRUE_MIN |
Example
Demonstates the underlying bit structure of the denorm_min() and prints the values:
#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
|
[static] | returns the smallest finite value of the given non-floating-point type, or the smallest positive normal value of the given floating-point type (public static member function) |
|
[static] | identifies the denormalization style used by the floating-point type (public static member constant) |
|
[static] (C++11) | returns the lowest finite value of the given type, i.e. the most negative value for signed types, 0 for unsigned types (public static member function) |
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