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

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