Split a single-precision floating-point number into a normalized fraction and an integer power of two.
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> Split a [single-precision floating-point number][ieee754] into a normalized fraction and an integer power of two.
``bash`
npm install @stdlib/math-base-special-frexpf
`javascript`
var frexpf = require( '@stdlib/math-base-special-frexpf' );
#### frexpf( x )
Splits a [single-precision floating-point number][ieee754] into a normalized fraction and an integer power of two.
`javascript`
var out = frexpf( 4.0 );
// returns [ 0.5, 3 ]
By default, the function returns the normalized fraction and the exponent as a two-element array. The normalized fraction and exponent satisfy the relation x = frac * 2^exp.
`javascript
var pow = require( '@stdlib/math-base-special-pow' );
var x = 4.0;
var out = frexpf( x );
// returns [ 0.5, 3 ]
var frac = out[ 0 ];
var exp = out[ 1 ];
var bool = ( x === frac * pow(2.0, exp) );
// returns true
`
If provided positive or negative zero, NaN, or positive or negative infinity, the function returns a two-element array containing the input value and an exponent equal to 0.
`javascript
var out = frexpf( 0.0 );
// returns [ 0.0, 0 ]
out = frexpf( -0.0 );
// returns [ -0.0, 0 ]
out = frexpf( NaN );
// returns [ NaN, 0 ]
out = frexpf( Infinity );
// returns [ Infinity, 0 ]
out = frexpf( -Infinity );
// returns [ -Infinity, 0 ]
`
For all other numeric input values, the [absolute value][@stdlib/math/base/special/absf] of the normalized fraction resides on the interval [0.5,1).
#### frexpf.assign( x, out, stride, offset )
Splits a [single-precision floating-point number][ieee754] into a normalized fraction and an integer power of two and assigns results to a provided output array.
`javascript
var Float32Array = require( '@stdlib/array-float32' );
var out = new Float32Array( 2 );
var y = frexpf.assign( 4.0, out, 1, 0 );
// returns
var bool = ( y === out );
// returns true
`
- Care should be taken when reconstituting a [single-precision floating-point number][ieee754] from a normalized fraction and an exponent. For example,
`javascript
var pow = require( '@stdlib/math-base-special-pow' );
var f32 = require( '@stdlib/number-float64-base-to-float32' );
var x = 1.7014118346046923e+38; // x ~ 2^127
var out = frexpf( x );
// returns [ 0.5, 128 ]
// Naive reconstitution:
var y = f32( out[ 0 ] * f32( pow( 2.0, out[ 1 ] ) ) );
// returns Infinity
// Account for 2^128 evaluating as infinity by recognizing 2^128 = 2^1 * 2^127:
y = f32( out[ 0 ] f32( pow( 2.0, out[1]-127 ) ) f32( pow( 2.0, 127 ) ) );
// returns 1.7014118346046923e+38
`
`javascript
var randu = require( '@stdlib/random-base-randu' );
var roundf = require( '@stdlib/math-base-special-roundf' );
var pow = require( '@stdlib/math-base-special-pow' );
var f32 = require( '@stdlib/number-float64-base-to-float32' );
var BIAS = require( '@stdlib/constants-float32-exponent-bias' );
var frexpf = require( '@stdlib/math-base-special-frexpf' );
var sign;
var frac;
var exp;
var x;
var f;
var v;
var i;
// Generate random numbers and break each into a normalized fraction and an integer power of two...
for ( i = 0; i < 100; i++ ) {
if ( randu() < 0.5 ) {
sign = f32( -1.0 );
} else {
sign = f32( 1.0 );
}
frac = f32( randu()*10.0 );
exp = roundf( randu()*76.0 ) - 38;
x = f32( sign frac f32( pow( 10.0, exp ) ) );
f = frexpf( x );
if ( f[ 1 ] > BIAS ) {
v = f32( f[ 0 ] f32( pow(2.0, f[1]-BIAS) ) f32( pow(2.0, BIAS) ) );
} else {
v = f32( f[ 0 ] * f32( pow( 2.0, f[ 1 ] ) ) );
}
console.log( '%d = %d * 2^%d = %d', x, f[ 0 ], f[ 1 ], v );
}
`
*
`c`
#include "stdlib/math/base/special/frexpf.h"
#### stdlib_base_frexpf( x, frac, exp )
Splits a [single-precision floating-point number][ieee754] into a normalized fraction and an integer power of two.
`c
#include
float frac;
int32_t exp;
stdlib_base_frexpf( 4.0f, &frac, &exp );
`
The function accepts the following arguments:
- x: [in] float input value.[out] float*
- frac: destination for the normalized fraction.[out] int32_t*
- exp: destination for the integer power of two.
`c`
void stdlib_base_frexpf( const float x, float frac, int32_t exp );
`c
#include "stdlib/math/base/special/frexpf.h"
#include
#include
#include
int main( void ) {
const float x[] = { 4.0f, 0.0f, -0.0f, 1.0f, -1.0f, 3.14f, -3.14f, 1.0e38f, -1.0e38f, 1.0f/0.0f, -1.0f/0.0f, 0.0f/0.0f };
float frac;
int32_t exp;
int i;
for ( i = 0; i < 12; i++ ) {
stdlib_base_frexpf( x[i], &frac, &exp );
printf( "x: %f => frac: %f, exp: %" PRId32 "\n", x[i], frac, exp );
}
}
`
*
This package is part of [stdlib][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][stdlib], see the main project [repository][stdlib].
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