ldexp

Article
2017-06-05

The new home for Visual Studio documentation is Visual Studio 2017 Documentation on docs.microsoft.com.

The latest version of this topic can be found at ldexp.

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

Syntax

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

Parameters

x
Floating-point value.

exp
Integer exponent.

Return Value

The ldexp function returns 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, ldexp always takes a double and an int and returns a double.

Requirements

Routine	C header	C++ header
`ldexp`, `ldexpf`, `ldexpl`	<math.h>	<cmath>

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

.NET Framework Equivalent

System::Math::Pow

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