NAME
trunc truncf
truncl — round to truncated
integer value
SYNOPSIS
#include
<math.h>
double trunc(double x); float truncf(float x); long double truncl(long double x);
DESCRIPTION
[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2024 defers to the ISO C standard.
These functions shall round their argument to the integer value, in floating format, nearest to but no larger in magnitude than the argument.
[MX] These functions may raise the inexact floating-point exception for finite non-integer arguments.
RETURN VALUE
Upon successful completion, these functions shall return the truncated integer value. [MX] The returned value shall be exact, shall be independent of the current rounding direction mode, and shall have the same sign as x.
[MX] If x is NaN, a NaN shall be returned.
If x is ±0 or ±Inf, x shall be returned.
ERRORS
No errors are defined.
EXAMPLES
None.
APPLICATION USAGE
The integral value returned by these functions need not be expressible as an intmax_t. The return value should be tested before assigning it to an integer type to avoid the undefined results of an integer overflow.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
XBD <math.h>
CHANGE HISTORY
First released in Issue 6. Derived from the ISO/IEC 9899:1999 (“ISO C99”) standard.
Issue 7
POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0684 [346] is applied.
Issue 8
Austin Group Defect 1302 is applied, aligning these functions with the ISO/IEC 9899:2018 standard.