simple-squiggle

A restricted subset of Squiggle
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combinations.js (2253B)

      1 "use strict";
      2 
      3 Object.defineProperty(exports, "__esModule", {
      4   value: true
      5 });
      6 exports.createCombinations = void 0;
      7 
      8 var _factory = require("../../utils/factory.js");
      9 
     10 var _combinations = require("../../plain/number/combinations.js");
     11 
     12 var name = 'combinations';
     13 var dependencies = ['typed'];
     14 var createCombinations = /* #__PURE__ */(0, _factory.factory)(name, dependencies, function (_ref) {
     15   var typed = _ref.typed;
     16 
     17   /**
     18    * Compute the number of ways of picking `k` unordered outcomes from `n`
     19    * possibilities.
     20    *
     21    * Combinations only takes integer arguments.
     22    * The following condition must be enforced: k <= n.
     23    *
     24    * Syntax:
     25    *
     26    *     math.combinations(n, k)
     27    *
     28    * Examples:
     29    *
     30    *    math.combinations(7, 5) // returns 21
     31    *
     32    * See also:
     33    *
     34    *    combinationsWithRep, permutations, factorial
     35    *
     36    * @param {number | BigNumber} n    Total number of objects in the set
     37    * @param {number | BigNumber} k    Number of objects in the subset
     38    * @return {number | BigNumber}     Number of possible combinations.
     39    */
     40   return typed(name, {
     41     'number, number': _combinations.combinationsNumber,
     42     'BigNumber, BigNumber': function BigNumberBigNumber(n, k) {
     43       var BigNumber = n.constructor;
     44       var result, i;
     45       var nMinusk = n.minus(k);
     46       var one = new BigNumber(1);
     47 
     48       if (!isPositiveInteger(n) || !isPositiveInteger(k)) {
     49         throw new TypeError('Positive integer value expected in function combinations');
     50       }
     51 
     52       if (k.gt(n)) {
     53         throw new TypeError('k must be less than n in function combinations');
     54       }
     55 
     56       result = one;
     57 
     58       if (k.lt(nMinusk)) {
     59         for (i = one; i.lte(nMinusk); i = i.plus(one)) {
     60           result = result.times(k.plus(i)).dividedBy(i);
     61         }
     62       } else {
     63         for (i = one; i.lte(k); i = i.plus(one)) {
     64           result = result.times(nMinusk.plus(i)).dividedBy(i);
     65         }
     66       }
     67 
     68       return result;
     69     } // TODO: implement support for collection in combinations
     70 
     71   });
     72 });
     73 /**
     74  * Test whether BigNumber n is a positive integer
     75  * @param {BigNumber} n
     76  * @returns {boolean} isPositiveInteger
     77  */
     78 
     79 exports.createCombinations = createCombinations;
     80 
     81 function isPositiveInteger(n) {
     82   return n.isInteger() && n.gte(0);
     83 }