simple-squiggle/node_modules/mathjs/lib/esm/plain/number/combinations.js

39 lines
1.2 KiB
JavaScript

import { isInteger } from '../../utils/number.js';
import { product } from '../../utils/product.js';
export function combinationsNumber(n, k) {
if (!isInteger(n) || n < 0) {
throw new TypeError('Positive integer value expected in function combinations');
}
if (!isInteger(k) || k < 0) {
throw new TypeError('Positive integer value expected in function combinations');
}
if (k > n) {
throw new TypeError('k must be less than or equal to n');
}
var nMinusk = n - k;
var answer = 1;
var firstnumerator = k < nMinusk ? nMinusk + 1 : k + 1;
var nextdivisor = 2;
var lastdivisor = k < nMinusk ? k : nMinusk; // balance multiplications and divisions to try to keep intermediate values
// in exact-integer range as long as possible
for (var nextnumerator = firstnumerator; nextnumerator <= n; ++nextnumerator) {
answer *= nextnumerator;
while (nextdivisor <= lastdivisor && answer % nextdivisor === 0) {
answer /= nextdivisor;
++nextdivisor;
}
} // for big n, k, floating point may have caused weirdness in remainder
if (nextdivisor <= lastdivisor) {
answer /= product(nextdivisor, lastdivisor);
}
return answer;
}
combinationsNumber.signature = 'number, number';