rint, rintf, rintl

项目
12/18/2017

The latest version of this topic can be found at rint, rintf, rintl.

Rounds a floating-point value to the nearest integer in floating-point format.

Syntax

double rint( double x );  
float rint( float x );  // C++ only  
long double rint( long double x );  // C++ only  
float rintf( float x );   
long double rintl( long double x );

Parameters

x
The floating-point value to round.

Return Value

The rint functions return a floating-point value that represents the nearest integer to x. Halfway values are rounded according to the current setting of the floating-point rounding mode, the same as the nearbyint functions. Unlike the nearbyint functions, the rint functions may raise the FE_INEXACT floating-point exception if the result differs in value from the argument. There is no error return.

Input	SEH Exception	`_matherr` Exception
± ∞, QNAN, IND	none	none
Denormals	EXCEPTION_FLT_UNDERFLOW	none

Remarks

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

Requirements

Function	C header	C++ header
`rint`, `rintf`, `rintl`	<math.h>	<cmath>

For additional compatibility information, see Compatibility.

Example

// crt_rint.c  
// Build with: cl /W3 /Tc crt_rint.c  
// This example displays the rounded results of  
// the floating-point values 2.499999, -2.499999,   
// 2.8, -2.8, 2.5 and -2.5.  
  
#include <math.h>  
#include <stdio.h>  
  
int main( void )  
{  
   double x = 2.499999;  
   float y = 2.8f;  
   long double z = 2.5;  
  
   printf("rint(%f) is %.0f\n", x, rint (x));  
   printf("rint(%f) is %.0f\n", -x, rint (-x));  
   printf("rintf(%f) is %.0f\n", y, rintf(y));  
   printf("rintf(%f) is %.0f\n", -y, rintf(-y));  
   printf("rintl(%Lf) is %.0Lf\n", z, rintl(z));  
   printf("rintl(%Lf) is %.0Lf\n", -z, rintl(-z));  
}

    rint
    (2.499999) is 2  
    rint
    (-2.499999) is -2  
    rintf
    (2.800000) is 3  
    rintf
    (-2.800000) is -3  
    rintl
    (2.500000) is 3  
    rintl
    (-2.500000) is -3

.NET Framework Equivalent

System::Math::Round

通过