simple-squiggle

A restricted subset of Squiggle
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probability.js (1867B)

      1 "use strict";
      2 
      3 Object.defineProperty(exports, "__esModule", {
      4   value: true
      5 });
      6 exports.gammaG = void 0;
      7 exports.gammaNumber = gammaNumber;
      8 exports.gammaP = void 0;
      9 
     10 var _number = require("../../utils/number.js");
     11 
     12 var _product = require("../../utils/product.js");
     13 
     14 /* eslint-disable no-loss-of-precision */
     15 function gammaNumber(n) {
     16   var x;
     17 
     18   if ((0, _number.isInteger)(n)) {
     19     if (n <= 0) {
     20       return isFinite(n) ? Infinity : NaN;
     21     }
     22 
     23     if (n > 171) {
     24       return Infinity; // Will overflow
     25     }
     26 
     27     return (0, _product.product)(1, n - 1);
     28   }
     29 
     30   if (n < 0.5) {
     31     return Math.PI / (Math.sin(Math.PI * n) * gammaNumber(1 - n));
     32   }
     33 
     34   if (n >= 171.35) {
     35     return Infinity; // will overflow
     36   }
     37 
     38   if (n > 85.0) {
     39     // Extended Stirling Approx
     40     var twoN = n * n;
     41     var threeN = twoN * n;
     42     var fourN = threeN * n;
     43     var fiveN = fourN * n;
     44     return Math.sqrt(2 * Math.PI / n) * Math.pow(n / Math.E, n) * (1 + 1 / (12 * n) + 1 / (288 * twoN) - 139 / (51840 * threeN) - 571 / (2488320 * fourN) + 163879 / (209018880 * fiveN) + 5246819 / (75246796800 * fiveN * n));
     45   }
     46 
     47   --n;
     48   x = gammaP[0];
     49 
     50   for (var i = 1; i < gammaP.length; ++i) {
     51     x += gammaP[i] / (n + i);
     52   }
     53 
     54   var t = n + gammaG + 0.5;
     55   return Math.sqrt(2 * Math.PI) * Math.pow(t, n + 0.5) * Math.exp(-t) * x;
     56 }
     57 
     58 gammaNumber.signature = 'number'; // TODO: comment on the variables g and p
     59 
     60 var gammaG = 4.7421875;
     61 exports.gammaG = gammaG;
     62 var gammaP = [0.99999999999999709182, 57.156235665862923517, -59.597960355475491248, 14.136097974741747174, -0.49191381609762019978, 0.33994649984811888699e-4, 0.46523628927048575665e-4, -0.98374475304879564677e-4, 0.15808870322491248884e-3, -0.21026444172410488319e-3, 0.21743961811521264320e-3, -0.16431810653676389022e-3, 0.84418223983852743293e-4, -0.26190838401581408670e-4, 0.36899182659531622704e-5];
     63 exports.gammaP = gammaP;