ldexp() — Multiply by a Power of Two

Format

#include <math.h>
double ldexp(double x, int exp);

Language Level: ANSI

Threadsafe: Yes.

Description

The ldexp() function calculates the value of x * (2^exp).

Return Value

The ldexp() function returns the value of x*(2^exp). If an overflow results, the function returns +HUGE_VAL for a large result or -HUGE_VAL for a small result, and sets errno to ERANGE.

Example that uses ldexp()

This example computes y as 1.5 times 2 to the fifth power (1.5*2⁵):

#include <math.h>
#include <stdio.h>
 
int main(void)
{
   double x, y;
   int p;
 
   x = 1.5;
   p = 5;
   y = ldexp(x,p);
 
   printf("%lf times 2 to the power of %d is %lf\n", x, p, y);
}
 
/********************  Output should be similar to:  **************
 
1.500000 times 2 to the power of 5 is 48.000000
*/

Related Information

• exp() — Calculate Exponential Function
• frexp() — Separate Floating-Point Value
• modf() — Separate Floating-Point Value
• <math.h>