Skip to content

Instantly share code, notes, and snippets.

@gus gus/life.kt
Created Jan 21, 2016

Embed
What would you like to do?
/**
* This is a straightforward implementation of The Game of Life
* See http://en.wikipedia.org/wiki/Conway's_Game_of_Life
*/
package life
/*
* A field where cells live. Effectively immutable
*/
class Field(
val width: Int,
val height: Int,
// This function tells the constructor which cells are alive
// if init(i, j) is true, the cell (i, j) is alive
init: (Int, Int) -> Boolean
) {
private val live: Array<Array<Boolean>> = Array(height) { i -> Array(width) { j -> init(i, j) } }
private fun liveCount(i: Int, j: Int)
= if (i in 0..height - 1 &&
j in 0..width - 1 &&
live[i][j]) 1 else 0
// How many neighbors of (i, j) are alive?
fun liveNeighbors(i: Int, j: Int) =
liveCount(i - 1, j - 1) +
liveCount(i - 1, j) +
liveCount(i - 1, j + 1) +
liveCount(i, j - 1) +
liveCount(i, j + 1) +
liveCount(i + 1, j - 1) +
liveCount(i + 1, j) +
liveCount(i + 1, j + 1)
// You can say field[i, j], and this function gets called
operator fun get(i: Int, j: Int) = live[i][j]
}
/**
* This function takes the present state of the field
* and returns a new field representing the next moment of time
*/
fun next(field: Field): Field {
return Field(field.width, field.height) { i, j ->
val n = field.liveNeighbors(i, j)
if (field[i, j])
// (i, j) is alive
n in 2..3 // It remains alive iff it has 2 or 3 neighbors
else
// (i, j) is dead
n == 3 // A new cell is born if there are 3 neighbors alive
}
}
/** A few colony examples here */
fun main(args: Array<String>) {
// Simplistic demo
runGameOfLife("***", 3)
// "Star burst"
runGameOfLife("""
_______
___*___
__***__
___*___
_______
""", 10)
// Stable colony
runGameOfLife("""
_____
__*__
_*_*_
__*__
_____
""", 3)
// Stable from the step 2
runGameOfLife("""
__**__
__**__
__**__
""", 3)
// Oscillating colony
runGameOfLife("""
__**____
__**____
____**__
____**__
""", 6)
// A fancier oscillating colony
runGameOfLife("""
-------------------
-------***---***---
-------------------
-----*----*-*----*-
-----*----*-*----*-
-----*----*-*----*-
-------***---***---
-------------------
-------***---***---
-----*----*-*----*-
-----*----*-*----*-
-----*----*-*----*-
-------------------
-------***---***---
-------------------
""", 10)
}
// UTILITIES
fun runGameOfLife(fieldText: String, steps: Int) {
var field = makeField(fieldText)
for (step in 1..steps) {
println("Step: $step")
for (i in 0..field.height - 1) {
for (j in 0..field.width - 1) {
print(if (field[i, j]) "*" else " ")
}
println("")
}
field = next(field)
}
}
fun makeField(s: String): Field {
val lines = s.replace(" ", "").split('\n').filter({ it.isNotEmpty() })
val longestLine = lines.toList().maxBy { it.length } ?: ""
return Field(longestLine.length, lines.size) { i, j -> lines[i][j] == '*' }
}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.