scalbn, scalbnf, scalbnl, scalbln, scalblnf, scalblnl

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

Syntax

double scalbn(
   double x,
   int exp
);
float scalbn(
   float x,
   int exp
);  // C++ only
long double scalbn(
   long double x,
   int exp
);  // C++ only
float scalbnf(
   float x,
   int exp
);
long double scalbnl(
   long double x,
   int exp
);

#define scalbn(X, INT) // Requires C11 or higher

double scalbln(
   double x,
   long exp
);

float scalblnf(
   float x,
   long exp
);
long double scalblnl(
   long double x,
   long exp
);

#define scalbln(X, LONG) // Requires C11 or higher

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

Parameters

x
Floating-point value.

exp
Integer exponent.

Return value

The scalbn functions return the value of x * FLT_RADIX^exp when successful. On overflow (depending on the sign of x), scalbn 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

FLT_RADIX is defined in <float.h> as the native floating-point radix; on binary systems, it has a value of 2, and scalbn is equivalent to ldexp.

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

If you use the <tgmath.h> scalbn() or scalbln macros, 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

Function	C header	C++ header
scalbn, scalbnf, scalbnl, scalbln, scalblnf, scalblnl	<math.h>	<cmath>
scalbn or scalbln macro	<tgmath.h>

For more compatibility information, see Compatibility.

Example

// crt_scalbn.c
// Compile using: cl /W4 crt_scalbn.c
#include <math.h>
#include <stdio.h>

int main( void )
{
   double x = 6.4, y;
   int p = 3;

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

Output

6.4 times FLT_RADIX to the power of 3 is 51.2

See also

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