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ldexp

Computes a real number from the mantissa and exponent.

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

Floating-point value.

exp

Integer exponent.

The ldexp function returns the value of x * 2exp if successful. On overflow (depending on the sign of x), ldexp returns +/– HUGE_VAL; the errno variable is set to ERANGE.

See _doserrno, errno, _sys_errlist, and _sys_nerr for more information on this, and other, return codes.

C++ allows overloading, so you can call overloads of ldexp. In a C program, ldexp always takes a double and an int and returns a double.

Routine

Required header

ldexp

<math.h>

For additional compatibility information, see Compatibility in the Introduction.

Libraries

All versions of the C run-time libraries.

// 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 );
}
4.0 times two to the power of 3 is 32.0
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