Created
September 2, 2011 00:44
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functional version of conway's life
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/** | |
* A functional Conway's game of life. | |
*/ | |
package object conway { | |
type Coord[A] = (Int, Int) => A | |
type Calculator = Coord[Coord[Boolean] => Boolean] | |
type Size = Int | |
val nextCell: Boolean => Int => Boolean = | |
old => mates => | |
if (mates > 3) false | |
else if (mates == 3) true | |
else (old && mates == 2) | |
val wrapper: Size => Int => Int = | |
size => i => | |
if (i < 0) size + i | |
else if (i >= size) i % size | |
else i | |
/** Function for working out the next generation's value for a board */ | |
val next: Size => Calculator = size => { | |
val wrap = wrapper(size) | |
(a, b) => { | |
val (x, y) = (wrap(a), wrap(b)) | |
val (l, r, u, d) = (wrap(x - 1), wrap(x + 1), wrap(y - 1), wrap(y + 1)) | |
val mates = List((l, u), (l, y), (l, d), (x, u), (x, d), (r, u), (r, y), (r, d)) | |
c => nextCell { c(x, y) } { mates filter { c.tupled } size } | |
} | |
} | |
implicit def asCoord[A](as: Array[Array[A]]): Coord[A] = (x, y) => as(x)(y) | |
val calculator: Size => Calculator = s => Array.tabulate(s, s) { next(s) } | |
val memo: Size => Coord[Boolean] => Coord[Boolean] = s => c => Array.tabulate(s, s) { c } | |
val generate: Calculator => Coord[Boolean] => Coord[Boolean] = c => old => (x, y) => c(x, y)(old) | |
val stream: Size => Coord[Boolean] => Stream[Coord[Boolean]] = size => init => { | |
val next = generate(calculator(size)) andThen memo(size) | |
def loop(old: Coord[Boolean]): Stream[Coord[Boolean]] = old #:: loop(next(old)) | |
loop(init) | |
} | |
val render: Size => Coord[Boolean] => String = size => c => { | |
val sb = new StringBuilder((size * size) + size, "") | |
for (x <- 0 until size) { | |
for (y <- 0 until size) sb.append(if (c(x, y)) "•" else " ") | |
sb.append("\n") | |
} | |
sb toString | |
} | |
val debug: Coord[Boolean] = (x, y) => { println("x: " + x + " y: " + y); ((x + y) & 1) == 0 } | |
} | |
package conway { | |
class Board(size: Size) extends Coord[Boolean] { | |
val board = Array.ofDim[Boolean](size, size) | |
def apply(x: Int) = (y: Int) => board(x)(y) | |
} | |
object Board { | |
import util.Random._ | |
def random(s: Size) = asCoord(Array.tabulate(s, s) { (_, _) => nextBoolean }) | |
} | |
} |
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