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/**
* @license Apache-2.0
*
* Copyright (c) 2018 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 and license were part of the original implementation available as part of [FreeBSD]{@link https://svnweb.freebsd.org/base/release/9.3.0/lib/msun/src/s_pow.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 getHighWord = require( '@stdlib/number/float64/base/get-high-word' );
// VARIABLES //
// 0x7fffffff = 2147483647 => 0 11111111111 11111111111111111111
var ABS_MASK = 0x7fffffff|0; // asm type annotation
// 0x3fefffff = 1072693247 => 0 01111111110 11111111111111111111 => biased exponent: 1022 = -1+1023 => 2^-1
var HIGH_MAX_NEAR_UNITY = 0x3fefffff|0; // asm type annotation
var HUGE = 1.0e300;
var TINY = 1.0e-300;
// MAIN //
/**
* Evaluates the exponential function when \\(|y| > 2^64\\).
*
* @private
* @param {number} x - base
* @param {number} y - exponent
* @returns {number} overflow or underflow result
*
* @example
* var v = pow( 9.0, 3.6893488147419103e19 );
* // returns Infinity
*
* @example
* var v = pow( -3.14, -3.6893488147419103e19 );
* // returns 0.0
*/
function pow( x, y ) {
var ahx;
var hx;
hx = getHighWord( x );
ahx = (hx & ABS_MASK);
if ( ahx <= HIGH_MAX_NEAR_UNITY ) {
if ( y < 0 ) {
// signal overflow...
return HUGE * HUGE;
}
// signal underflow...
return TINY * TINY;
}
// `x` has a biased exponent greater than or equal to `0`...
if ( y > 0 ) {
// signal overflow...
return HUGE * HUGE;
}
// signal underflow...
return TINY * TINY;
}
// EXPORTS //
module.exports = pow;
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