Press n or j to go to the next uncovered block, b, p or k for the previous block.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 | 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 2811x 2811x 2811x 2811x 2811x 2810x 2811x 2x 2x 2811x 401x 401x 401x 2811x 398x 398x 398x 2811x 1x 1x 1x 2811x 2006x 2006x 2004x 2006x 3x 3x 3x 2x 2x 3x 2811x 3x 3x 3x 2005x 2811x 1x 1x 2004x 2811x 1x 1x 1x 1x 1x | /**
* @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 original C++ code and copyright notice are from the [Boost library]{@link http://www.boost.org/doc/libs/1_85_0/boost/math/special_functions/powm1.hpp}. The implementation follows the original, but has been modified for JavaScript.
*
* ```text
* (C) Copyright John Maddock 2006.
*
* Use, modification and distribution are subject to the
* Boost Software License, Version 1.0. (See accompanying file
* LICENSE or copy at http://www.boost.org/LICENSE_1_0.txt)
* ```
*/
'use strict';
// MODULES //
var isnan = require( '@stdlib/math/base/assert/is-nan' );
var isinfinite = require( '@stdlib/math/base/assert/is-infinite' );
var abs = require( '@stdlib/math/base/special/abs' );
var expm1 = require( '@stdlib/math/base/special/expm1' );
var ln = require( '@stdlib/math/base/special/ln' );
var pow = require( '@stdlib/math/base/special/pow' );
var trunc = require( '@stdlib/math/base/special/trunc' );
// MAIN //
/**
* Evaluates `bˣ - 1`.
*
* @param {number} b - base
* @param {number} x - exponent
* @returns {number} function value
*
* @example
* var y = powm1( 2.0, 3.0 );
* // returns 7.0
*
* @example
* var y = powm1( 4.0, 0.5 );
* // returns 1.0
*
* @example
* var y = powm1( 0.0, 100.0 );
* // returns -1.0
*
* @example
* var y = powm1( 100.0, 0.0 );
* // returns 0.0
*
* @example
* var y = powm1( 0.0, 0.0 );
* // returns 0.0
*
* @example
* var y = powm1( 3.141592653589793, 5.0 );
* // returns ~305.0197
*
* @example
* var y = powm1( NaN, 3.0 );
* // returns NaN
*
* @example
* var y = powm1( 5.0, NaN );
* // returns NaN
*/
function powm1( b, x ) {
var result;
var y;
if (
isnan( b ) ||
isnan( x )
) {
return NaN;
}
if ( x === 0.0 ) {
// Any number raised to zero (including 0) is always 1 => b^0 - 1 = 0
return 0.0;
}
if ( b === 0.0 ) {
// Zero raised to any number (except 0) is always zero => 0^x - 1 = -1
return -1.0;
}
if ( b < 0.0 && x%2.0 === 0 ) {
// If `x` is even, recognize that `(-b)**x == (b)**x`...
b = -b;
}
if ( b > 0.0 ) {
if (
abs( x*(b-1.0) ) < 0.5 ||
abs( x ) < 0.2
) {
// No good/quick approximation for ln(b)*x, so we have to evaluate...
y = ln( b ) * x;
if ( y < 0.5 ) {
return expm1( y );
}
}
} else if ( trunc( x ) !== x ) {
// Exponentiation would yield a complex result...
return NaN;
}
result = pow( b, x ) - 1.0;
if ( isinfinite( result ) || isnan( result ) ) {
return NaN;
}
return result;
}
// EXPORTS //
module.exports = powm1;
|