ieee

Name

logb, logbf, logbl, scalb, scalbf, scalbl, significand, significandf, significandl
- IEEE test functions

Library

libm.lib

Synopsis

#include <math.h>

double logb (double x);

float logbf (float x);

long double logbl (long double x);

double scalb (double x, double n);

float scalbf (float x, float n);

long double scalbl (long double x, long double n);

double significand (double x);

float significandf (float x);

long double significandl (long double x);

Detailed description

These functions allow users to test conformance to -ieee754. Their use is not otherwise recommended.

logb (x);
and logbf (x);
return x ’s exponent n, a signed integer converted to double-precision floating-point. logb (±oo);
= +oo; logb (0);

= -oo

scalb (x, n);
and scalbf (x, n);
return x *(2** n) computed by exponent manipulation. If n is not an integer, ±oo, or an NaN, the result is unspecified.

significand (x);
and significandf (x);
return sig, where x = sig * 2** n with 1 <= sig < 2. significand (x);
and significandf (x);
are not defined when x is 0, ±oo, or NaN. Here , long double version function are just aliases to their corresponding double version apis.

Examples

#include <math.h>
int main( )
{
   double e = 2.718282;
   /*Logb(), logbf() and logbl() */
   y = logb( e );
   printf( "logb( %f) = %f\n", e, y );
   y = logbf( e );
   printf( "logbf( %f) = %f\n", e, y );
   y = logbl( e );
   printf( "logbl( %f) = %f\n\n", e, y );
   /*scalb(), scalbf() and scalbl()*/
   double x1 = 0.8, x2 = 4.0 ;
   y = scalb( x1, x2 );
   printf( "scalb( %f, %f) = %f\n", x1, x2, y );
   y = scalbf( x1, x2 );
   printf( "scalbf( %f, %f) = %f\n", x1, x2, y );
   y = scalbl( x1, x2 );
   printf( "scalbl( %f, %f) = %f\n", x1, x2, y );
   /*significand(), significandf() and significandl()*/
   x2 = 4.0 ;
   y = significand( x2 );
   printf( "significand(%f)  = %f\n",  x2, y );
   y = significandf( x2 );
   printf( "significandf(%f) = %f\n",x2, y );
   y = significandl( x2 );
   printf( "significandl(%f) = %f\n",x2, y );
}

Output

logb( 2.718282) = 1.000000
logbf( 2.718282) = 1.000000
logbl( 2.718282) = 1.000000
scalb( 0.8, 4.0 ) = 12.800000
scalbf( 0.8, 4.0 ) = 12.800000
scalbl( 0.8, 4.0 ) = 12.800000
significand ( 4.0) = 1.000000
significandf( 4.0) = 1.000000
significandl( 4.0) = 1.000000

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