Conway's game of life

[Paul via Digitalmars-d-learn]

On Monday, 2 February 2015 at 16:58:43 UTC, bearophile wrote:
>
> The quality of the D GC is not important for a simple Life 
> implementation, you just need two arrays.

Here's my 30 minute sandwich-break version, sorry it's not very 
arractive 'D'...

import std.stdio;
import std.random;


void main(){

	enum WORLDSIZE = 20;
	enum INITIALPOP = 70;	//experimental
	enum DEAD = 0;
	enum ALIVE = 1;

	int world[WORLDSIZE][WORLDSIZE];
	int buffer[WORLDSIZE][WORLDSIZE];
	
	//sprinkle life
	foreach(i; 0..INITIALPOP){
		//find an empty cell
		int rX, rY;
		do{
			rX = uniform(0, WORLDSIZE);
			rY = uniform(0, WORLDSIZE);
		} while(world[rX][rY] == ALIVE);
		world[rX][rY] = ALIVE;
	}
			
	//loop forever
	while (true){
	
		//work on the buffer
		buffer = world;

		foreach(x; 0..WORLDSIZE){
			foreach(y; 0..WORLDSIZE){

				int neighbourCount;
									
				//get index to left, right, above and below current cell, 
wrapping if necessary
				int left = (x == 0) ? WORLDSIZE-1 : x-1;
				int right = (x == (WORLDSIZE-1) ) ? 0 : x+1;
				int top = (y == 0) ? WORLDSIZE-1 : y-1;
				int bottom = (y == (WORLDSIZE-1) ) ? 0 : y+1;
				
				//add up surrounding cells
				neighbourCount += world[left][y];
				neighbourCount += world[left][top];
				neighbourCount += world[left][bottom];
				neighbourCount += world[x][top];
				neighbourCount += world[x][bottom];
				neighbourCount += world[right][top];
				neighbourCount += world[right][y];
				neighbourCount += world[right][bottom];
					

				//if this cell is alive
				if( world[x][y] == ALIVE){
					//decide what to do
					switch(neighbourCount){
						case 2:
						buffer[x][y] = ALIVE;
						break;
						case 3:
						buffer[x][y] = ALIVE;
						break;
						default:
						buffer[x][y] = DEAD;
					}
				}
				else{
					//just like today's news, newborn has three parents!			
					if(neighbourCount == 3) buffer[x][y] = ALIVE;
				}
			}		
		}
		
		//update world with contents of buffer
		world = buffer;
		
		//show current state of world with fancy graphics :P
		foreach(x; 0..WORLDSIZE){
			foreach(y; 0..WORLDSIZE){
				write( world[x][y] == ALIVE ? "X" : "." );
			}
			writeln();
		}

		readln();
		
	}//end loop
}