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Diffstat (limited to 'node_modules/locutus/c/math/frexp.js')
| -rw-r--r-- | node_modules/locutus/c/math/frexp.js | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/node_modules/locutus/c/math/frexp.js b/node_modules/locutus/c/math/frexp.js new file mode 100644 index 0000000..876e2f5 --- /dev/null +++ b/node_modules/locutus/c/math/frexp.js @@ -0,0 +1,75 @@ +"use strict"; + +module.exports = function frexp(arg) { + // discuss at: http://locutus.io/c/frexp/ + // original by: Oskar Larsson Högfeldt (http://oskar-lh.name/) + // note 1: Instead of + // note 1: double frexp( double arg, int* exp ); + // note 1: this is built as + // note 1: [double, int] frexp( double arg ); + // note 1: due to the lack of pointers in JavaScript. + // note 1: See code comments for further information. + // example 1: frexp(1) + // returns 1: [0.5, 1] + // example 2: frexp(1.5) + // returns 2: [0.75, 1] + // example 3: frexp(3 * Math.pow(2, 500)) + // returns 3: [0.75, 502] + // example 4: frexp(-4) + // returns 4: [-0.5, 3] + // example 5: frexp(Number.MAX_VALUE) + // returns 5: [0.9999999999999999, 1024] + // example 6: frexp(Number.MIN_VALUE) + // returns 6: [0.5, -1073] + // example 7: frexp(-Infinity) + // returns 7: [-Infinity, 0] + // example 8: frexp(-0) + // returns 8: [-0, 0] + // example 9: frexp(NaN) + // returns 9: [NaN, 0] + + // Potential issue with this implementation: + // the precisions of Math.pow and the ** operator are undefined in the ECMAScript standard, + // however, sane implementations should give the same results for Math.pow(2, <integer>) operations + + // Like frexp of C and std::frexp of C++, + // but returns an array instead of using a pointer argument for passing the exponent result. + // Object.is(n, frexp(n)[0] * 2 ** frexp(n)[1]) for all number values of n except when Math.isFinite(n) && Math.abs(n) > 2**1023 + // Object.is(n, (2 * frexp(n)[0]) * 2 ** (frexp(n)[1] - 1)) for all number values of n + // Object.is(n, frexp(n)[0]) for these values of n: 0, -0, NaN, Infinity, -Infinity + // Math.abs(frexp(n)[0]) is >= 0.5 and < 1.0 for any other number-type value of n + // See http://en.cppreference.com/w/c/numeric/math/frexp for a more detailed description + + arg = Number(arg); + + var result = [arg, 0]; + + if (arg !== 0 && Number.isFinite(arg)) { + var absArg = Math.abs(arg); + // Math.log2 was introduced in ES2015, use it when available + var log2 = Math.log2 || function log2(n) { + return Math.log(n) * Math.LOG2E; + }; + var exp = Math.max(-1023, Math.floor(log2(absArg)) + 1); + var x = absArg * Math.pow(2, -exp); + + // These while loops compensate for rounding errors that sometimes occur because of ECMAScript's Math.log2's undefined precision + // and also works around the issue of Math.pow(2, -exp) === Infinity when exp <= -1024 + while (x < 0.5) { + x *= 2; + exp--; + } + while (x >= 1) { + x *= 0.5; + exp++; + } + + if (arg < 0) { + x = -x; + } + result[0] = x; + result[1] = exp; + } + return result; +}; +//# sourceMappingURL=frexp.js.map
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