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- 'use strict';
- // based on Shewchuk's algorithm for exactly floating point addition
- // adapted from https://github.com/tc39/proposal-math-sum/blob/3513d58323a1ae25560e8700aa5294500c6c9287/polyfill/polyfill.mjs
- var $ = require('../internals/export');
- var uncurryThis = require('../internals/function-uncurry-this');
- var iterate = require('../internals/iterate');
-
- var $RangeError = RangeError;
- var $TypeError = TypeError;
- var $Infinity = Infinity;
- var $NaN = NaN;
- var abs = Math.abs;
- var pow = Math.pow;
- var push = uncurryThis([].push);
-
- var POW_2_1023 = pow(2, 1023);
- var MAX_SAFE_INTEGER = pow(2, 53) - 1; // 2 ** 53 - 1 === 9007199254740992
- var MAX_DOUBLE = Number.MAX_VALUE; // 2 ** 1024 - 2 ** (1023 - 52) === 1.79769313486231570815e+308
- var MAX_ULP = pow(2, 971); // 2 ** (1023 - 52) === 1.99584030953471981166e+292
-
- var NOT_A_NUMBER = {};
- var MINUS_INFINITY = {};
- var PLUS_INFINITY = {};
- var MINUS_ZERO = {};
- var FINITE = {};
-
- // prerequisite: abs(x) >= abs(y)
- var twosum = function (x, y) {
- var hi = x + y;
- var lo = y - (hi - x);
- return { hi: hi, lo: lo };
- };
-
- // `Math.sumPrecise` method
- // https://github.com/tc39/proposal-math-sum
- $({ target: 'Math', stat: true, forced: true }, {
- // eslint-disable-next-line max-statements -- ok
- sumPrecise: function sumPrecise(items) {
- var numbers = [];
- var count = 0;
- var state = MINUS_ZERO;
-
- iterate(items, function (n) {
- if (++count >= MAX_SAFE_INTEGER) throw new $RangeError('Maximum allowed index exceeded');
- if (typeof n != 'number') throw new $TypeError('Value is not a number');
- if (state !== NOT_A_NUMBER) {
- // eslint-disable-next-line no-self-compare -- NaN check
- if (n !== n) state = NOT_A_NUMBER;
- else if (n === $Infinity) state = state === MINUS_INFINITY ? NOT_A_NUMBER : PLUS_INFINITY;
- else if (n === -$Infinity) state = state === PLUS_INFINITY ? NOT_A_NUMBER : MINUS_INFINITY;
- else if ((n !== 0 || (1 / n) === $Infinity) && (state === MINUS_ZERO || state === FINITE)) {
- state = FINITE;
- push(numbers, n);
- }
- }
- });
-
- switch (state) {
- case NOT_A_NUMBER: return $NaN;
- case MINUS_INFINITY: return -$Infinity;
- case PLUS_INFINITY: return $Infinity;
- case MINUS_ZERO: return -0;
- }
-
- var partials = [];
- var overflow = 0; // conceptually 2 ** 1024 times this value; the final partial is biased by this amount
- var x, y, sum, hi, lo, tmp;
-
- for (var i = 0; i < numbers.length; i++) {
- x = numbers[i];
- var actuallyUsedPartials = 0;
- for (var j = 0; j < partials.length; j++) {
- y = partials[j];
- if (abs(x) < abs(y)) {
- tmp = x;
- x = y;
- y = tmp;
- }
- sum = twosum(x, y);
- hi = sum.hi;
- lo = sum.lo;
- if (abs(hi) === $Infinity) {
- var sign = hi === $Infinity ? 1 : -1;
- overflow += sign;
-
- x = (x - (sign * POW_2_1023)) - (sign * POW_2_1023);
- if (abs(x) < abs(y)) {
- tmp = x;
- x = y;
- y = tmp;
- }
- sum = twosum(x, y);
- hi = sum.hi;
- lo = sum.lo;
- }
- if (lo !== 0) partials[actuallyUsedPartials++] = lo;
- x = hi;
- }
- partials.length = actuallyUsedPartials;
- if (x !== 0) push(partials, x);
- }
-
- // compute the exact sum of partials, stopping once we lose precision
- var n = partials.length - 1;
- hi = 0;
- lo = 0;
-
- if (overflow !== 0) {
- var next = n >= 0 ? partials[n] : 0;
- n--;
- if (abs(overflow) > 1 || (overflow > 0 && next > 0) || (overflow < 0 && next < 0)) {
- return overflow > 0 ? $Infinity : -$Infinity;
- }
- // here we actually have to do the arithmetic
- // drop a factor of 2 so we can do it without overflow
- // assert(abs(overflow) === 1)
- sum = twosum(overflow * POW_2_1023, next / 2);
- hi = sum.hi;
- lo = sum.lo;
- lo *= 2;
- if (abs(2 * hi) === $Infinity) {
- // rounding to the maximum value
- if (hi > 0) {
- return (hi === POW_2_1023 && lo === -(MAX_ULP / 2) && n >= 0 && partials[n] < 0) ? MAX_DOUBLE : $Infinity;
- } return (hi === -POW_2_1023 && lo === (MAX_ULP / 2) && n >= 0 && partials[n] > 0) ? -MAX_DOUBLE : -$Infinity;
- }
-
- if (lo !== 0) {
- partials[++n] = lo;
- lo = 0;
- }
-
- hi *= 2;
- }
-
- while (n >= 0) {
- sum = twosum(hi, partials[n--]);
- hi = sum.hi;
- lo = sum.lo;
- if (lo !== 0) break;
- }
-
- if (n >= 0 && ((lo < 0 && partials[n] < 0) || (lo > 0 && partials[n] > 0))) {
- y = lo * 2;
- x = hi + y;
- if (y === x - hi) hi = x;
- }
-
- return hi;
- }
- });
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