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round, roundf, roundl

Visual Studio 2013

Rounds a floating-point value to the nearest integer.

double round( 
   double x 
);
float round(
   float x
);  // C++ only
long double round(
   long double x
);  // C++ only
float roundf(
   float x
);
long double roundl(
   long double x
);
x

The floating-point value to round.

The round functions return a floating-point value that represents the nearest integer to x. Halfway values are rounded away from zero, regardless of the setting of the floating-point rounding mode. There is no error return.

Input

SEH Exception

Matherr Exception

± QNAN,IND

none

_DOMAIN

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

Routine

Required header

round, roundf, roundl

<math.h>

For additional compatibility information, see Compatibility.

// crt_round.c
// Build with: cl /W3 /Tc crt_round.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("round(%f) is %.0f\n", x, round(x));
   printf("round(%f) is %.0f\n", -x, round(-x));
   printf("roundf(%f) is %.0f\n", y, roundf(y));
   printf("roundf(%f) is %.0f\n", -y, roundf(-y));
   printf("roundl(%Lf) is %.0Lf\n", z, roundl(z));
   printf("roundl(%Lf) is %.0Lf\n", -z, roundl(-z));
}
round(2.499999) is 2
round(-2.499999) is -2
roundf(2.800000) is 3
roundf(-2.800000) is -3
roundl(2.500000) is 3
roundl(-2.500000) is -3
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