std::trunc,std::truncf,std::truncl (3) - Linux Manuals
Defined in header <cmath>
float trunc ( float arg ); (1) (since C++11)
float truncf( float arg );
double trunc ( double arg ); (2) (since C++11)
long double trunc ( long double arg ); (3) (since C++11)
long double truncl( long double arg );
double trunc ( IntegralType arg ); (4) (since C++11)
1-3) Computes the nearest integer not greater in magnitude than arg.
4) A set of overloads or a function template accepting an argument of any integral_type. Equivalent to 2) (the argument is cast to double).
arg - floating point value
Errors are reported as specified in math_errhandling.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
* The current rounding_mode has no effect.
* If arg is ±∞, it is returned, unmodified
* If arg is ±0, it is returned, unmodified
* If arg is NaN, NaN is returned
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.
// Run this code
floorl nearest integer not greater than the given value
ceill nearest integer not less than the given value
llroundl nearest integer, rounding away from zero in halfway cases