c/numeric/math/trunc

@1-3@ Computes the nearest integer not greater in magnitude than. @4@ Type-generic macro: If has type,  is called. Otherwise, if has integer type or the type,  is called. Otherwise, is called.

Return value
If no errors occur, the nearest integer value not greater in magnitude than (in other words,  rounded towards zero), is returned.

Error handling
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 is ±∞, it is returned, unmodified
 * If is ±0, it is returned, unmodified
 * If arg is NaN, NaN is returned