Package Exports
- @stdlib/math-base-special-ldexp
- @stdlib/math-base-special-ldexp/dist
- @stdlib/math-base-special-ldexp/dist/index.js
- @stdlib/math-base-special-ldexp/lib/index.js
This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (@stdlib/math-base-special-ldexp) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.
Readme
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ldexp
Multiply a double-precision floating-point number by an integer power of two.
Installation
npm install @stdlib/math-base-special-ldexpUsage
var ldexp = require( '@stdlib/math-base-special-ldexp' );ldexp( frac, exp )
Multiplies a double-precision floating-point number by an integer power of two (i.e., x = frac * 2^exp).
var x = ldexp( 0.5, 3 ); // => 0.5 * 2^3 = 0.5 * 8
// returns 4.0
x = ldexp( 4.0, -2 ); // => 4 * 2^(-2) = 4 * (1/4)
// returns 1.0If frac equals positive or negative zero, NaN, or positive or negative infinity, the function returns a value equal to frac.
var x = ldexp( 0.0, 20 );
// returns 0.0
x = ldexp( -0.0, 39 );
// returns -0.0
x = ldexp( NaN, -101 );
// returns NaN
x = ldexp( Infinity, 11 );
// returns Infinity
x = ldexp( -Infinity, -118 );
// returns -InfinityNotes
- This function is the inverse of
frexp.
Examples
var randu = require( '@stdlib/random-base-randu' );
var round = require( '@stdlib/math-base-special-round' );
var pow = require( '@stdlib/math-base-special-pow' );
var frexp = require( '@stdlib/math-base-special-frexp' );
var ldexp = require( '@stdlib/math-base-special-ldexp' );
var sign;
var frac;
var exp;
var x;
var f;
var v;
var i;
for ( i = 0; i < 100; i++ ) {
if ( randu() < 0.5 ) {
sign = -1.0;
} else {
sign = 1.0;
}
// Generate a random number:
frac = randu() * 10.0;
exp = round( randu()*616.0 ) - 308;
x = sign * frac * pow( 10.0, exp );
// Break the number into a normalized fraction and an integer power of two:
f = frexp( x );
// Reconstitute the original number:
v = ldexp( f[ 0 ], f[ 1 ] );
console.log( '%d = %d * 2^%d = %d', x, f[ 0 ], f[ 1 ], v );
}C APIs
Usage
#include "stdlib/math/base/special/ldexp.h"stdlib_base_ldexp( frac, exp )
Multiplies a double-precision floating-point number by an integer power of two (i.e., x = frac * 2^exp).
double x = stdlib_base_ldexp( 0.5, 3 ); // => 0.5 * 2^3 = 0.5 * 8
// returns 4.0The function accepts the following arguments:
- frac:
[in] doubleinput value. - exp:
[in] int32_tinteger power of two.
double stdlib_base_ldexp( const double frac, const int32_t exp );Examples
#include "stdlib/math/base/special/ldexp.h"
#include "stdlib/math/base/special/frexp.h"
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <inttypes.h>
#include <math.h>
static double rand_double() {
int r = rand();
return (double)r / ( (double)RAND_MAX + 1.0 );
}
int main( void ) {
double sign;
double frac;
int32_t exp;
double x;
double v;
int i;
for ( i = 0; i < 100; i++ ) {
if ( rand_double() < 0.5 ) {
sign = -1.0;
} else {
sign = 1.0;
}
// Generate a random number:
frac = rand_double() * 10.0;
exp = (int32_t)( rand_double()*616.0 ) - 308;
x = sign * frac * pow( 10.0, exp );
// Break the number into a normalized fraction and an integer power of two:
stdlib_base_frexp( x, &frac, &exp );
// Reconstitute the original number:
v = stdlib_base_ldexp( frac, exp );
printf( "%e = %lf * 2^%" PRId32 " = %e\n", x, frac, exp, v );
}
}Notice
This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.
For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.
Community
License
See LICENSE.
Copyright
Copyright © 2016-2024. The Stdlib Authors.