trunc, truncf, truncl - cppreference.com (original) (raw)

Defined in header <math.h>
float truncf( float arg ); (1) (since C99)
double trunc( double arg ); (2) (since C99)
long double truncl( long double arg ); (3) (since C99)
Defined in header <tgmath.h>
#define trunc( arg ) (4) (since C99)

1-3) Computes the nearest integer not greater in magnitude than arg.

  1. Type-generic macro: If arg has type long double, truncl is called. Otherwise, if arg has integer type or the type double, trunc is called. Otherwise, truncf is called.

Contents

[edit] Parameters

arg - floating-point value

[edit] Return value

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

Return value

math-trunc.svg

Argument

[edit] Error handling

Errors are reported as specified in math_errhandling.

If the implementation supports IEEE floating-point arithmetic (IEC 60559):

[edit] Notes

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 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.

[edit] Example

#include <math.h> #include <stdio.h>   int main(void) { printf("trunc(+2.7) = %+.1f\n", trunc(+2.7)); printf("trunc(-2.7) = %+.1f\n", trunc(-2.7)); printf("trunc(-0.0) = %+.1f\n", trunc(-0.0)); printf("trunc(-Inf) = %+f\n", trunc(-INFINITY)); }

Possible output:

trunc(+2.7) = +2.0 trunc(-2.7) = -2.0 trunc(-0.0) = -0.0 trunc(-Inf) = -inf

[edit] References

[edit] See also