[79a0317] | 1 | 'use strict';
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| 2 | // based on Shewchuk's algorithm for exactly floating point addition
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| 3 | // adapted from https://github.com/tc39/proposal-math-sum/blob/3513d58323a1ae25560e8700aa5294500c6c9287/polyfill/polyfill.mjs
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| 4 | var $ = require('../internals/export');
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| 5 | var uncurryThis = require('../internals/function-uncurry-this');
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| 6 | var iterate = require('../internals/iterate');
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| 7 |
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| 8 | var $RangeError = RangeError;
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| 9 | var $TypeError = TypeError;
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| 10 | var $Infinity = Infinity;
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| 11 | var $NaN = NaN;
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| 12 | var abs = Math.abs;
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| 13 | var pow = Math.pow;
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| 14 | var push = uncurryThis([].push);
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| 15 |
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| 16 | var POW_2_1023 = pow(2, 1023);
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| 17 | var MAX_SAFE_INTEGER = pow(2, 53) - 1; // 2 ** 53 - 1 === 9007199254740992
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| 18 | var MAX_DOUBLE = Number.MAX_VALUE; // 2 ** 1024 - 2 ** (1023 - 52) === 1.79769313486231570815e+308
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| 19 | var MAX_ULP = pow(2, 971); // 2 ** (1023 - 52) === 1.99584030953471981166e+292
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| 20 |
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| 21 | var NOT_A_NUMBER = {};
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| 22 | var MINUS_INFINITY = {};
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| 23 | var PLUS_INFINITY = {};
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| 24 | var MINUS_ZERO = {};
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| 25 | var FINITE = {};
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| 26 |
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| 27 | // prerequisite: abs(x) >= abs(y)
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| 28 | var twosum = function (x, y) {
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| 29 | var hi = x + y;
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| 30 | var lo = y - (hi - x);
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| 31 | return { hi: hi, lo: lo };
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| 32 | };
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| 33 |
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| 34 | // `Math.sumPrecise` method
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| 35 | // https://github.com/tc39/proposal-math-sum
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| 36 | $({ target: 'Math', stat: true }, {
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| 37 | // eslint-disable-next-line max-statements -- ok
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| 38 | sumPrecise: function sumPrecise(items) {
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| 39 | var numbers = [];
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| 40 | var count = 0;
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| 41 | var state = MINUS_ZERO;
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| 42 |
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| 43 | iterate(items, function (n) {
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| 44 | if (++count >= MAX_SAFE_INTEGER) throw new $RangeError('Maximum allowed index exceeded');
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| 45 | if (typeof n != 'number') throw new $TypeError('Value is not a number');
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| 46 | if (state !== NOT_A_NUMBER) {
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| 47 | // eslint-disable-next-line no-self-compare -- NaN check
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| 48 | if (n !== n) state = NOT_A_NUMBER;
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| 49 | else if (n === $Infinity) state = state === MINUS_INFINITY ? NOT_A_NUMBER : PLUS_INFINITY;
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| 50 | else if (n === -$Infinity) state = state === PLUS_INFINITY ? NOT_A_NUMBER : MINUS_INFINITY;
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| 51 | else if ((n !== 0 || (1 / n) === $Infinity) && (state === MINUS_ZERO || state === FINITE)) {
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| 52 | state = FINITE;
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| 53 | push(numbers, n);
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| 54 | }
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| 55 | }
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| 56 | });
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| 57 |
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| 58 | switch (state) {
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| 59 | case NOT_A_NUMBER: return $NaN;
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| 60 | case MINUS_INFINITY: return -$Infinity;
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| 61 | case PLUS_INFINITY: return $Infinity;
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| 62 | case MINUS_ZERO: return -0;
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| 63 | }
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| 64 |
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| 65 | var partials = [];
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| 66 | var overflow = 0; // conceptually 2 ** 1024 times this value; the final partial is biased by this amount
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| 67 | var x, y, sum, hi, lo, tmp;
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| 68 |
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| 69 | for (var i = 0; i < numbers.length; i++) {
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| 70 | x = numbers[i];
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| 71 | var actuallyUsedPartials = 0;
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| 72 | for (var j = 0; j < partials.length; j++) {
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| 73 | y = partials[j];
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| 74 | if (abs(x) < abs(y)) {
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| 75 | tmp = x;
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| 76 | x = y;
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| 77 | y = tmp;
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| 78 | }
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| 79 | sum = twosum(x, y);
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| 80 | hi = sum.hi;
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| 81 | lo = sum.lo;
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| 82 | if (abs(hi) === $Infinity) {
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| 83 | var sign = hi === $Infinity ? 1 : -1;
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| 84 | overflow += sign;
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| 85 |
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| 86 | x = (x - (sign * POW_2_1023)) - (sign * POW_2_1023);
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| 87 | if (abs(x) < abs(y)) {
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| 88 | tmp = x;
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| 89 | x = y;
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| 90 | y = tmp;
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| 91 | }
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| 92 | sum = twosum(x, y);
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| 93 | hi = sum.hi;
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| 94 | lo = sum.lo;
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| 95 | }
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| 96 | if (lo !== 0) partials[actuallyUsedPartials++] = lo;
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| 97 | x = hi;
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| 98 | }
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| 99 | partials.length = actuallyUsedPartials;
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| 100 | if (x !== 0) push(partials, x);
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| 101 | }
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| 102 |
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| 103 | // compute the exact sum of partials, stopping once we lose precision
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| 104 | var n = partials.length - 1;
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| 105 | hi = 0;
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| 106 | lo = 0;
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| 107 |
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| 108 | if (overflow !== 0) {
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| 109 | var next = n >= 0 ? partials[n] : 0;
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| 110 | n--;
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| 111 | if (abs(overflow) > 1 || (overflow > 0 && next > 0) || (overflow < 0 && next < 0)) {
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| 112 | return overflow > 0 ? $Infinity : -$Infinity;
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| 113 | }
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| 114 | // here we actually have to do the arithmetic
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| 115 | // drop a factor of 2 so we can do it without overflow
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| 116 | // assert(abs(overflow) === 1)
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| 117 | sum = twosum(overflow * POW_2_1023, next / 2);
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| 118 | hi = sum.hi;
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| 119 | lo = sum.lo;
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| 120 | lo *= 2;
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| 121 | if (abs(2 * hi) === $Infinity) {
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| 122 | // rounding to the maximum value
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| 123 | if (hi > 0) {
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| 124 | return (hi === POW_2_1023 && lo === -(MAX_ULP / 2) && n >= 0 && partials[n] < 0) ? MAX_DOUBLE : $Infinity;
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| 125 | } return (hi === -POW_2_1023 && lo === (MAX_ULP / 2) && n >= 0 && partials[n] > 0) ? -MAX_DOUBLE : -$Infinity;
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| 126 | }
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| 127 |
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| 128 | if (lo !== 0) {
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| 129 | partials[++n] = lo;
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| 130 | lo = 0;
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| 131 | }
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| 132 |
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| 133 | hi *= 2;
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| 134 | }
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| 135 |
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| 136 | while (n >= 0) {
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| 137 | sum = twosum(hi, partials[n--]);
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| 138 | hi = sum.hi;
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| 139 | lo = sum.lo;
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| 140 | if (lo !== 0) break;
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| 141 | }
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| 142 |
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| 143 | if (n >= 0 && ((lo < 0 && partials[n] < 0) || (lo > 0 && partials[n] > 0))) {
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| 144 | y = lo * 2;
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| 145 | x = hi + y;
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| 146 | if (y === x - hi) hi = x;
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| 147 | }
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| 148 |
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| 149 | return hi;
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| 150 | }
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| 151 | });
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