ldexp.md

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ldexp, ldexpf, ldexpl	API reference for ldexp, ldexpf, and ldexpl; which multiplies a floating-point number by an integral power of two.	9/1/2020	ldexp ldexpf ldexpl _ldexpl _o_ldexp	msvcrt.dll msvcr80.dll msvcr90.dll msvcr100.dll msvcr100_clr0400.dll msvcr110.dll msvcr110_clr0400.dll msvcr120.dll msvcr120_clr0400.dll ucrtbase.dll api-ms-win-crt-math-l1-1-0.dll	DLLExport	apiref	ldexp ldexpf ldexpl _ldexpl	calculating real numbers computing real numbers mantissas, floating-point variables ldexp function ldexpf function ldexpl function exponent, floating-point numbers floating-point functions, mantissa and exponent	aa7f5310-3879-4f63-ae74-86a39fbdedfa

ldexp, ldexpf, ldexpl

Multiplies a floating-point number by an integral power of two.

Syntax

double ldexp(
   double x,
   int exp
);
float ldexpf(
   float x,
   int exp
);
long double ldexpl(
   long double x,
   int exp
);
#define ldexp(X, INT) // Requires C11 or higher

float ldexp(
   float x,
   int exp
);  // C++ only
long double ldexp(
   long double x,
   int exp
);  // C++ only

Parameters

x
Floating-point value.

exp
Integer exponent.

Return value

The ldexp functions return the value of x * 2^exp if successful. On overflow, and depending on the sign of x, ldexp returns +/- HUGE_VAL; the errno value is set to ERANGE.

For more information about errno and possible error return values, see errno, _doserrno, _sys_errlist, and _sys_nerr.

Remarks

Because C++ allows overloading, you can call overloads of ldexp that take float or long double types. In a C program, unless you're using the <tgmath.h> macro to call this function, ldexp always takes a double and an int and returns a double.

If you use the <tgmath.h> ldexp() 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	C header	C++ header
ldexp, ldexpf, ldexpl	<math.h>	<cmath>
ldexp macro	<tgmath.h>

For compatibility information, see Compatibility.

Example

// crt_ldexp.c

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

int main( void )
{
   double x = 4.0, y;
   int p = 3;

   y = ldexp( x, p );
   printf( "%2.1f times two to the power of %d is %2.1f\n", x, p, y );
}

Output

4.0 times two to the power of 3 is 32.0

See also

Math and floating-point support
frexp
modf, modff, modfl