All files / math/base/special/expf/lib expmultif.js

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/**
* @license Apache-2.0
*
* Copyright (c) 2025 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*    http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*
* ## Notice
*
* The following copyrights, licenses, and long comment were part of the original implementation available as part of{@link https://svnweb.freebsd.org/base/release/12.2.0/lib/msun/src/e_expf.c}, The implementation follows the original, but has been modified for JavaScript.
*
* ```text
* Copyright (C) 2004 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ```
*/
 
'use strict';
 
// MODULES //
 
var ldexpf = require( '@stdlib/math/base/special/ldexpf' );
var f32 = require( '@stdlib/number/float64/base/to-float32' );
var polyvalP = require( './polyval_p.js' );
 
 
// VARIABLES //
 
var ONE = f32( 1.0 );
var TWO = f32( 2.0 );
 
 
// MAIN //
 
/**
* Computes \\(e^{r} 2^k\\) for a single-precision floating-point number, where \\(r = \mathrm{hi} - \mathrm{lo}\\) and \\(|r| \leq \ln(2)/2\\).
*
* @private
* @param {number} hi - upper bound
* @param {number} lo - lower bound
* @param {integer} k - power of 2
* @returns {number} function value
*/
function expmultif( hi, lo, k ) {
	var r;
	var t;
	var c;
	var y;
 
	r = f32( hi - lo );
	t = f32( r * r );
	c = f32( r - f32( t*polyvalP( t ) ) );
	y = f32( ONE - f32( f32( lo - f32( f32(r*c)/f32(TWO-c) ) ) - hi ) );
 
	return ldexpf( y, k );
}
 
 
// EXPORTS //
 
module.exports = expmultif;