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* @license Apache-2.0
*
* Copyright (c) 2024 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.
*/
'use strict';
// MODULES //
var FLOAT64_EPS = require( '@stdlib/constants/float64/eps' );
var FLOAT64_SMALLEST_NORMAL = require( '@stdlib/constants/float64/smallest-normal' );
var FLOAT64_MIN_EXPONENT = require( '@stdlib/constants/float64/min-base2-exponent' );
var FLOAT64_MAX_EXPONENT = require( '@stdlib/constants/float64/max-base2-exponent' );
var FLOAT64_MAX = require( '@stdlib/constants/float64/max' );
var FLOAT64_PRECISION = require( '@stdlib/constants/float64/precision' );
var lowercase = require( '@stdlib/string/base/lowercase' );
// VARIABLES //
var RADIX = 2.0;
// MAIN //
/**
* Determines double-precision floating-point machine parameters.
*
* ## Notes
*
* - The `cmach` parameter is a string which specifies the double-precision machine parameter to be returned. The function recognizes the following characters:
*
* - `'E'`/`'e'`: (eps) relative machine precision.
* - `'S'`/`'s'`: (sfmin) safe minimum such that `1/sfmin` does not overflow.
* - `'B'`/`'b'`: (base) base of the machine (also known as the floating-point radix).
* - `'P'`/`'p'`: (prec) `eps*base`.
* - `'N'`/`'n'`: (t) number of (base) digits in the mantissa.
* - `'R'`/`'r'`: (rnd) `1.0` when rounding occurs in addition and `0.0` otherwise.
* - `'M'`/`'m'`: (emin) minimum exponent before (gradual) underflow.
* - `'U'`/`'u'`: (rmin) underflow threshold.
* - `'L'`/`'l'`: (emax) largest exponent before overflow.
* - `'O'`/`'o'`: (rmax) overflow threshold.
*
* @param {string} cmach - specifies the value to be returned
* @returns {number} machine parameter
*
* @example
* var out = dlamch( 'E' );
* // returns ~1.1102230246251565e-016
*
* out = dlamch( 'S' );
* // returns ~2.2250738585072014e-308
*
* out = dlamch( 'B' );
* // returns 2.0
*/
function dlamch( cmach ) {
cmach = lowercase( cmach.charAt( 0 ) );
if ( cmach === 'e' ) {
return FLOAT64_EPS * 0.5;
}
if ( cmach === 's' ) {
return FLOAT64_SMALLEST_NORMAL;
}
if ( cmach === 'b' ) {
return RADIX;
}
if ( cmach === 'p' ) {
return FLOAT64_EPS * 0.5 * RADIX;
}
if ( cmach === 'n' ) {
return FLOAT64_PRECISION;
}
if ( cmach === 'r' ) {
return 1.0;
}
if ( cmach === 'm' ) {
return FLOAT64_MIN_EXPONENT + 1;
}
if ( cmach === 'u' ) {
return FLOAT64_SMALLEST_NORMAL;
}
if ( cmach === 'l' ) {
return FLOAT64_MAX_EXPONENT + 1;
}
if ( cmach === 'o' ) {
return FLOAT64_MAX;
}
return 0.0;
}
// EXPORTS //
module.exports = dlamch;
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