`lround`, `lroundf`, `lroundl`, `llround`, `llroundf`, `llroundl`

2022-12-02

Rounds a floating-point value to the nearest integer.

Syntax

long lround(
   double x
);
long lround(
   float x
);  // C++ only
long lround(
   long double x
);  // C++ only
long lroundf(
   float x
);
long lroundl(
   long double x
);
long long llround(
   double x
);
long long llround(
   float x
);  // C++ only
long long llround(
   long double x
);  // C++ only
long long llroundf(
   float x
);
long long llroundl(
   long double x
);
#define lround(X) // Requires C11 or later

Parameters

x
The floating-point value to round.

Return value

The lround and llround functions return the nearest long or long long integer to x. Halfway values are rounded away from zero, regardless of the setting of the floating-point rounding mode. There's no error return.

Input	SEH exception	`_matherr` exception
± QNaN, IND	none	`_DOMAIN`

Remarks

Because C++ allows overloading, you can call lround or llround overloads that take and return float and long double values. In a C program, unless you're using the <tgmath.h> macro to call this function, lround and llround always take and return a double.

If you use the <tgmath.h> lround() macro, the type of the argument determines which version of the function is selected. See Type-generic math for details.

By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.

Requirements

Routine	Required header
`lround`, `lroundf`, `lroundl`, `llround`, `llroundf`, `llroundl`	<math.h>
`lround` macro	<tgmath.h>

For more compatibility information, see Compatibility.

Example

// crt_lround.c
// Build with: cl /W4 /Tc crt_lround.c
// This example displays the rounded results of
// the floating-point values 2.499999, -2.499999,
// 2.8, -2.8, 3.5 and -3.5.

#include <math.h>
#include <stdio.h>

int main( void )
{
   double x = 2.499999;
   float y = 2.8f;
   long double z = 3.5L;

   printf("lround(%f) is %d\n", x, lround(x));
   printf("lround(%f) is %d\n", -x, lround(-x));
   printf("lroundf(%f) is %d\n", y, lroundf(y));
   printf("lroundf(%f) is %d\n", -y, lroundf(-y));
   printf("lroundl(%Lf) is %d\n", z, lroundl(z));
   printf("lroundl(%Lf) is %d\n", -z, lroundl(-z));
}

lround(2.499999) is 2
lround(-2.499999) is -2
lroundf(2.800000) is 3
lroundf(-2.800000) is -3
lroundl(3.500000) is 4
lroundl(-3.500000) is -4

Chia sẻ qua

lround, lroundf, lroundl, llround, llroundf, llroundl