Defined in header
float trunc( float arg );
double trunc( double arg );
long double trunc( long double arg );
double trunc( Integral arg );
|arg||-||floating point value|
If no errors occur, the nearest integer value not greater in magnitude than
arg (in other words,
arg rounded towards zero), is returned.
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.
argis ±∞, it is returned, unmodified
argis ±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.
trunc(+2.7) = 2.000000 trunc(-2.9) = -2.000000 trunc(-0.0) = -0.000000 trunc(-Inf) = -inf
| nearest integer not greater than the given value |
| nearest integer not less than the given value |
| nearest integer, rounding away from zero in halfway cases |
C documentation for trunc