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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 copyright, license, and long comment were part of the original implementation available as part of [FreeBSD]{@link https://svnweb.freebsd.org/base/release/12.2.0/lib/msun/src/s_sinf.c}. The implementation follows the original, but has been modified for JavaScript.
*
* ```text
* Copyright (C) 1993 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 float64ToFloat32 = require( '@stdlib/number/float64/base/to-float32' );
var floorf = require( '@stdlib/math/base/special/floorf' );
var ldexpf = require( '@stdlib/math/base/special/ldexpf' );
var FLOAT32_MAX = require( '@stdlib/constants/float32/max' );
var FLOAT32_MAX_LN = require( '@stdlib/constants/float32/max-ln' );
var FLOAT32_MIN_LN = require( '@stdlib/constants/float32/min-ln' );
var FLOAT32_LOG2E = require( '@stdlib/constants/float32/log2-e' );
var polyvalP = require( './polyval_p.js' );
// VARIABLES //
var LN2_HI = 0.693359375;
var LN2_LO = -2.12194440e-4;
// MAIN //
/**
* Evaluates the natural exponential function of single-precision floating-point numbers.
*
* @param {number} x - input value
* @returns {number} function value
*
* @example
* var v = expf( 4.0 );
* // returns ~54.59815
*
* @example
* var v = expf( -9.0 );
* // returns ~1.234098e-4
*
* @example
* var v = expf( 0.0 );
* // returns 1.0
*
* @example
* var v = expf( NaN );
* // returns NaN
*/
function expf( x ) {
var z;
var n;
var p;
var y;
if ( x > FLOAT32_MAX_LN ) {
return FLOAT32_MAX;
}
if ( x < FLOAT32_MIN_LN ) {
return 0.0;
}
// e^x = e^(nln2 + g) = e^(nln2) * e^g = 2^n * e^g.
z = floorf( ( float64ToFloat32( FLOAT32_LOG2E * float64ToFloat32( x ) ) + 0.5 ) );
x -= float64ToFloat32( z * LN2_HI );
x -= float64ToFloat32( z * LN2_LO );
x = float64ToFloat32( x );
n = z;
z = float64ToFloat32( x * x );
p = polyvalP( x );
y = float64ToFloat32(p * z) + x + 1.0;
return ldexpf( y, n );
}
// EXPORTS //
module.exports = expf;
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