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 * 2exp 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