double trunc ( double num );
constexpr /*floating-point-type*/
trunc ( /*floating-point-type*/ num );
float truncf( float num );
(2) (since C++11)long double truncl( long double num );
(3) (since C++11)constexpr /*deduced-simd-t*/<V>
template< class Integer >
double trunc ( Integer num );
1-3) Computes the nearest integer not greater in magnitude than num. The library provides overloads of std::trunc
for all cv-unqualified floating-point types as the type of the parameter.(since C++23)
A) Additional overloads are provided for all integer types, which are treated as double.
(since C++11) [edit] Parameters num - floating-point or integer value [edit] Return valueIf no errors occur, the nearest integer value not greater in magnitude than num (in other words, num rounded towards zero) is returned.
Return value
num
[edit] Error handlingErrors are reported as specified in math_errhandling.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
FE_INEXACT may be (but isn't required to be) raised when truncating a non-integer finite value.
The largest representable floating-point values are exact integers in all standard floating-point formats, so this function never overflows on its own; however the result may overflow any integer type (including std::intmax_t), when stored in an integer variable.
The implicit conversion from floating-point to integral types also rounds towards zero, but is limited to the values that can be represented by the target type.
The additional overloads are not required to be provided exactly as (A). They only need to be sufficient to ensure that for their argument num of integer type, std::trunc(num) has the same effect as std::trunc(static_cast<double>(num)).
[edit] ExamplePossible output:
trunc(+2.7) == +2 trunc(-2.9) == -2 trunc(+0.7) == +0 trunc(-0.9) == -0 trunc(+0) == +0 trunc(+0) == +0 trunc(-inf) == -inf trunc(+inf) == +inf trunc(-nan) == -nan trunc(+nan) == +nan[edit] See also
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