Conway's Game of Life

conway.php

<?php

$height = 20;
$width = 40;
$live_seeds = 20;
$delay = 1000000;

$empty_grid = fn(): array => array_fill(0, $height, array_fill(0, $width, false));

$random_percent = fn(): float => rand(0, 100) / 100;

$seed_cell = fn(float $x_seed, float $y_seed): array => [ floor($x_seed * $height), floor($y_seed * $width) ];

$seed_pairs = function (int $max_seeds, array $seeds = []) use ($seed_cell, $random_percent, &$seed_pairs): array {
    if (count($seeds) === $max_seeds) {
        return $seeds;
    }

    do {
        $cell = $seed_cell($random_percent(), $random_percent());
    } while (in_array($cell, $seeds));

    return $seed_pairs($max_seeds, [ ...$seeds, $cell ]);
};

$populate_grid = function (array $grid, array $pairs) use (&$populate_grid): array {
    if (empty($pairs)) {
        return $grid;
    }

    $pair = array_slice($pairs, 0, 1)[0];
    $pairs = array_slice($pairs, 1);
    [ $x, $y ] = $pair;
    $grid[$x][$y] = true;
    return $populate_grid($grid, $pairs);
};

$initialize_grid = fn(): array => $populate_grid($empty_grid(), $seed_pairs($live_seeds));

$print_cell = fn(bool $cell): string => $cell ? 'O' : '-';

$print_grid = function (array $grid) use ($print_cell): void {
    foreach ($grid as $row) {
        foreach ($row as $cell) {
            echo $print_cell($cell);
        }
        echo PHP_EOL;
    }
};

$next_cell = function (int $x, int $y) use ($height, $width): ?array {
    if ($x < $height) {
        return [ $x + 1, $y ];
    }

    $y++;
    if ($y < $width) {
        return [ 0, $y ];
    }

    return null;
};

$live_neighbors = function (array $grid, int $x, int $y): int {
    $xmo = $x - 1;
    $xpo = $x + 1;
    $ymo = $y - 1;
    $ypo = $y + 1;
    $cell = fn(int $cx, int $cy): ?bool => $grid[$cx][$cy] ?? null;
    return count(array_filter([
        $cell($xmo, $ymo),
        $cell($x, $ymo),
        $cell($xpo, $ymo),
        $cell($xmo, $y),
        $cell($x, $y),
        $cell($xpo, $y),
        $cell($xmo, $ypo),
        $cell($x, $ypo),
        $cell($xpo, $ypo),
    ]));
};

$iterate_cell = function (array $grid, int $x, int $y) use ($live_neighbors): bool {
    $neighbors = $live_neighbors($grid, $x, $y);
    return $neighbors === 2 || $neighbors === 3;
};

$iterate_grid = function (array $grid, array $cell = [ 0, 0 ]) use ($next_cell, $iterate_cell, &$iterate_grid): array {
    [ $x, $y ] = $cell;
    $grid[$x][$y] = $iterate_cell($grid, $x, $y);
    $cell = $next_cell($x, $y);
    return $cell ? $iterate_grid($grid, $cell) : $grid;
};

$grid = $initialize_grid();
while (true) {
    echo shell_exec('clear');
    $print_grid($grid);
    $grid = $iterate_grid($grid);
    usleep($delay);
}