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frand

Pure functions for deterministically generating pseudorandom numbers

This module contains a small collection of simple "generators", i.e. pure functions that transform a seed (really just a Number) into a predictable output value.

You will usually want to change the seed after every use (typically by incrementing it) unless your goal is to get the same results multiple times.

usage

const { percent, integer, boolean } = require('frand')
const { choose, shuffle } = require('frand/array')

`percent(seed)`

Generate a number between 0 and 1 using seed, exclusively.

if (percent(seed++) < 0.1) {
  money.type = 'gold'
} else {
  money.type = 'copper'
}

1 is not included in the set of possible return values, so this function is essentially a seedable version of Math.random().

`integer(min, max, seed)`

Generate an integer between min and max using seed, inclusively.

function roll(seed) {
  return integer(1, 6, seed)
}

Unlike percent, the upper number (max) is included in the set of possible return values.

`boolean(seed)`

Choose either true and false based on the given seed.

if (boolean(seed++)) {
  for (var connector of connectors) {
    floors.push(connector)
  }
} else {
  var connector = choose(connectors, seed++)
  doors.push(connector)
}

The following two methods can be found in frand/array.