trunc, truncf, truncl

Article
06/05/2017

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Determines the nearest integer that is less than or equal to the specified floating-point value.

Syntax

double trunc(  
   double x  
);  
  
float trunc(  
   float x  
); //C++ only  
  
long double trunc(  
   long double x  
); //C++ only  
  
float trunc(  
   float x  
); //C++ only  
  
long double truncl(  
   long double x  
);

Parameters

[in] x
The value to truncate.

Return Value

If successful, returns an integer value of x, rounded towards zero.

Otherwise, may return one of the following:

Issue	Return
`x` = ±INFINITY	x
`x` = ±0	x
`x` = NaN	NaN

Errors are reported as specified in _matherr.

Remarks

Because C++ allows overloading, you can call overloads of trunc that take and return float and long double types. In a C program, trunc always takes and returns a double.

Because the largest floating-point values are exact integers, this function will not overflow on its own. However, you may cause the function to overflow by returning a value into an integer type.

You can also round down by implicitly converting from floating-point to integral; however, doing so is limited to the values that can be stored in the target type.

Requirements

Function	C header	C++ header
`trunc`, `truncf`, `truncl`	<math.h>	<cmath>

For additional compatibility information, see Compatibility.

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