mirror of
https://github.com/codeninjasllc/codecombat.git
synced 2024-11-25 08:38:09 -05:00
34 lines
1,014 B
CoffeeScript
34 lines
1,014 B
CoffeeScript
# http://coffeescriptcookbook.com/chapters/math/generating-predictable-random-numbers
|
|
class Rand
|
|
@className: 'Rand'
|
|
# If created without a seed, uses current time as seed.
|
|
constructor: (@seed) ->
|
|
# Knuth and Lewis' improvements to Park and Miller's LCPRNG
|
|
@multiplier = 1664525
|
|
@modulo = 4294967296 # 2**32-1
|
|
@offset = 1013904223
|
|
unless @seed? and 0 <= seed < @modulo
|
|
@seed = (new Date().valueOf() * new Date().getMilliseconds()) % @modulo
|
|
|
|
# sets new seed value, even handling negative numbers
|
|
setSeed: (seed) ->
|
|
@seed = ((seed % @modulo) + @modulo) % @modulo
|
|
|
|
# return a random integer 0 <= n < @modulo
|
|
randn: =>
|
|
# new_seed = (a * seed + c) % m
|
|
@seed = (@multiplier * @seed + @offset) % @modulo
|
|
|
|
# return a random float 0 <= f < 1.0
|
|
randf: =>
|
|
@randn() / @modulo
|
|
|
|
# return a random int 0 <= f < n
|
|
rand: (n) =>
|
|
Math.floor @randf() * n
|
|
|
|
# return a random int min <= f < max
|
|
rand2: (min, max) =>
|
|
min + @rand max - min
|
|
|
|
module.exports = Rand
|