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random-ordered-pair.js
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random-ordered-pair.js
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/**
* Pandemonium Random Ordered Pair
* ================================
*
* Random ordered pair function.
*/
/**
* Creating a function returning a random ordered pair of the given array.
*
* @param {function} rng - RNG function returning uniform random.
* @return {function} - The created function.
*/
function createRandomOrderedPair(rng) {
/**
* Random ordered pair function.
*
* @param {array|number} array - Target array or length of the array.
* @return {number}
*/
return function (array) {
var needItems = typeof array !== 'number';
var n = needItems ? array.length : array;
if (n < 2)
throw new Error(
'pandemonium/random-ordered-pair: cannot draw a random ordered pair for length < 2.'
);
var i = Math.floor(rng() * n);
var o = 1 + Math.floor(rng() * (n - 1));
var j = (i + o) % n;
if (needItems) return [array[i], array[j]];
return [i, j];
};
}
/**
* Default random ordered pair using `Math.random`.
*/
var randomOrderedPair = createRandomOrderedPair(Math.random);
/**
* Exporting.
*/
randomOrderedPair.createRandomOrderedPair = createRandomOrderedPair;
module.exports = randomOrderedPair;