Binary Logarithm

Evaluate the binary logarithm.

The binary logarithm (logarithm with base 2) is defined for any positive real number as

Usage

var log2 = require( '@stdlib/math/base/special/log2' );

log2( x )

Evaluates the binary logarithm.

var v = log2( 4.0 );
// returns 2.0

v = log2( 0.0 );
// returns -Infinity

v = log2( Infinity );
// returns Infinity

v = log2( NaN );
// returns NaN

For negative numbers, the binary logarithm is not defined.

var v = log2( -4.0 );
// returns NaN

Examples

var randu = require( '@stdlib/random/base/randu' );
var round = require( '@stdlib/math/base/special/round' );
var log2 = require( '@stdlib/math/base/special/log2' );

var x;
var i;

for ( i = 0; i < 100; i++ ) {
    x = round( randu() * 100.0 );
    console.log( 'log2(%d) = %d', x, log2( x ) );
}

C APIs

Usage

#include "stdlib/math/base/special/log2.h"

stdlib_base_log2( x )

Evaluates the binary logarithm.

double out = stdlib_base_log2( 4.0 );
// returns 2.0

The function accepts the following arguments:

x: [in] double input value.

double stdlib_base_log2( const double x );

Examples

#include "stdlib/math/base/special/log2.h"
#include <stdlib.h>
#include <stdio.h>

int main( void ) {
    double x;
    double v;
    int i;
    for ( i = 0; i < 100; i++ ) {
        x = ( ( (double)rand() / (double)RAND_MAX ) * 100.0 );
        v = stdlib_base_log( x );
        printf( "log2(%lf) = %lf\n", x, v );
    }
}