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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 original C code, long comment, copyright, license, and constants are from [Cephes]{@link http://www.netlib.org/cephes}. The implementation follows the original, but has been modified for JavaScript.
*
* ```text
* Copyright 1984, 1987, 1988, 1992 by Stephen L. Moshier
*
* Some software in this archive may be from the book _Methods and Programs for Mathematical Functions_ (Prentice-Hall or Simon & Schuster International, 1989) or from the Cephes Mathematical Library, a commercial product. In either event, it is copyrighted by the author. What you see here may be used freely but it comes with no support or guarantee.
*
* Stephen L. Moshier
* moshier@na-net.ornl.gov
* ```
*/
'use strict';
// MODULES //
var floorf = require( '@stdlib/math/base/special/floorf' );
var ldexpf = require( '@stdlib/math/base/special/ldexpf' );
var isnanf = require( '@stdlib/math/base/assert/is-nanf' );
var PINF = require( '@stdlib/constants/float32/pinf' );
var f32 = require( '@stdlib/number/float64/base/to-float32' );
var toInt32 = require( '@stdlib/number/float64/base/to-int32' );
var polyval = require( './polyval.js' );
// VARIABLES //
var LOG210 = 3.32192809488736234787;
var LG102A = 0.30078125000000000000;
var LG102B = 0.000248745663981195213739;
var MAXL10 = 38.230809449325611792;
// MAIN //
/**
* Returns `10` raised to the `x` power of a single-precision floating-point number.
*
* ## Method
*
* - Range reduction is accomplished by expressing the argument as \\( 10^x = 2^n 10^f \\), with \\( |f| < 0.5 log_{10}(2) \\). The Pade' form
*
* ```tex
* 1 + f * P(f)
* ```
*
* is used to approximate \\( 10^f \\).
*
* ## Notes
*
* - Relative error:
*
* | arithmetic | domain | # trials | peak | rms |
* |:----------:|:-----------:|:--------:|:-------:|:-------:|
* | IEEE | -38,+38 | 100000 | 9.8e-8 | 2.8e-8 |
*
* @param {number} x - input value
* @returns {number} function value
*
* @example
* var v = exp10f( 3.0 );
* // returns 1000.0
*
* @example
* var v = exp10f( -9.0 );
* // returns ~1.0e-9
*
* @example
* var v = exp10f( 0.0 );
* // returns 1.0
*
* @example
* var v = exp10f( NaN );
* // returns NaN
*/
function exp10f( x ) {
var xc;
var px;
var n;
if ( isnanf( x ) ) {
return x;
}
if ( x === 0.0 ) {
return 1.0;
}
if ( x > MAXL10 ) {
return PINF;
}
if ( x < (-1 * MAXL10) ) {
return 0.0;
}
// Express 10^x = 10^g 2^n = 10^g 10^( n log10(2) ) = 10^( g + n log10(2) )
px = floorf( ( LOG210 * f32(x) ) + 0.5 );
n = toInt32( px );
xc = f32(x);
xc = xc - ( px * LG102A );
xc = xc - ( px * LG102B );
// Polynomial approximation for fractional part: 10^f ≈ 1 + f * P(f)
px = xc * polyval( xc );
xc = 1.0 + px;
// Multiply by power of 2:
return ldexpf( xc, n );
}
// EXPORTS //
module.exports = exp10f;
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