std::numeric_limits<T>::is_exact

 

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C numeric limits interface
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std::numeric_limits

Static constants

numeric_limits::is_specialized

numeric_limits::is_signed

numeric_limits::is_integer

numeric_limits::is_exact

numeric_limits::has_infinity

numeric_limits::has_quiet_NaN

numeric_limits::has_signaling_NaN

numeric_limits::has_denorm

numeric_limits::has_denorm_loss

numeric_limits::round_style

numeric_limits::is_iec559

numeric_limits::is_bounded

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numeric_limits::max_digits10 (C++11)

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numeric_limits::min_exponent10

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numeric_limits::max_exponent10

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numeric_limits::tinyness_before

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numeric_limits::min

numeric_limits::lowest (C++11)

numeric_limits::max

numeric_limits::epsilon

numeric_limits::round_error

numeric_limits::infinity

numeric_limits::quiet_NaN

numeric_limits::signaling_NaN

numeric_limits::denorm_min

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float_round_style

float_denorm_style

 

static const bool is_exact;		(until C++11)
static constexpr bool is_exact;			(since C++11)

See More

The value of std::numeric_limits<T>::is_exact is true for all arithmetic types T that use exact representation.

Standard specializations

T	value of std::numeric_limits<T>::is_exact
/* non-specialized */	false
bool	true
char	true
signed char	true
unsigned char	true
wchar_t	true
char8_t (since C++20)	true
char16_t (since C++11)	true
char32_t (since C++11)	true
short	true
unsigned short	true
int	true
unsigned int	true
long	true
unsigned long	true
long long (since C++11)	true
unsigned long long (since C++11)	true
float	false
double	false
long double	false

Notes

While all fundamental types T for which std::numeric_limits<T>::is_exact == true are integer types, a library may define exact types that are not integers, e.g., a rational arithmetic type representing fractions.

Example

Run this code

#include <limits>
#include <ratio>

template <typename... Types>
constexpr bool exact = (std::numeric_limits<Types>::is_exact and ...);

static_assert(exact<
    bool, char, signed char, unsigned char, wchar_t, char8_t, char16_t, char32_t, short,
    unsigned short, int, unsigned int, long, unsigned long, long long, unsigned long long
>);

template <typename... Types>
constexpr bool not_exact = ((not std::numeric_limits<Types>::is_exact) and ...);

static_assert(not_exact<std::exa, float, double, long double>);

int main() {}

See also

is_integer [static]	identifies integer types (public static member constant)
is_signed [static]	identifies signed types (public static member constant)
is_bounded [static]	identifies types that represent a finite set of values (public static member constant)