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7e958639b2
As in python random module. It can be useful for levels instead "someArray[@world.rand.rand(someArray.length)]".
56 lines
1.5 KiB
CoffeeScript
56 lines
1.5 KiB
CoffeeScript
# http://coffeescriptcookbook.com/chapters/math/generating-predictable-random-numbers
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class Rand
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@className: 'Rand'
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# If created without a seed, uses current time as seed.
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constructor: (@seed) ->
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# Knuth and Lewis' improvements to Park and Miller's LCPRNG
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@multiplier = 1664525
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@modulo = 4294967296 # 2**32-1
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@offset = 1013904223
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unless @seed? and 0 <= @seed < @modulo
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@seed = (new Date().valueOf() * new Date().getMilliseconds()) % @modulo
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# sets new seed value, even handling negative numbers
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setSeed: (seed) ->
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@seed = ((seed % @modulo) + @modulo) % @modulo
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# return a random integer 0 <= n < @modulo
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randn: =>
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# new_seed = (a * seed + c) % m
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@seed = (@multiplier * @seed + @offset) % @modulo
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# return a random float 0 <= f < 1.0
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randf: =>
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@randn() / @modulo
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# return a random int 0 <= f < n
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rand: (n) =>
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Math.floor @randf() * n
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# return a random int min <= f < max
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rand2: (min, max) =>
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min + @rand max - min
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# return a random float min <= f < max
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randf2: (min, max) =>
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min + @randf() * (max - min)
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# return a random float within range around x
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randfRange: (x, range) =>
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x + (-0.5 + @randf()) * range
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# shuffle array in place, and also return it
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shuffle: (arr) =>
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return arr unless arr.length > 2
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for i in [arr.length-1 .. 1]
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j = Math.floor @randf() * (i - 1)
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t = arr[j]
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arr[j] = arr[i]
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arr[i] = t
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arr
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choice: (arr) =>
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return arr[@rand arr.length]
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module.exports = Rand
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