『ラングトンのアリの描画』投稿

<?php  
function lang_ant($w, $h)  
{  
	$world = array_fill(0, $h, array_fill(0, $w, 1));  
	$x = (int)($w/2);  
	$y = (int)($h/2);  
	$dct = 0; /* 0:N 1:E 2:S 3:W */  
	$stp_ant = array(‘$x++;’, ‘$y++;’, ‘$x–;’, ‘$y–;’);  
	$chg_dct = array(‘$dct = (((++$dct)%4)+2)%4;’, ‘$dct = (++$dct)%4;’);  
	$print_world = array(‘0’, ‘&nbsp;’);  
  
	for ( $i = 0; $i < 20000; $i++) {  
		eval($chg_dct[$world[$y][$x]]);  
		eval($stp_ant[$dct]);  
		if ($x<0 || $w<=$x || $y<0 || $h<=$y) {  
			break;  
		}  
		$world[$y][$x] = (++$world[$y][$x])%2;  
	}  
	foreach ( $world as $cels) {  
		foreach ($cels as $cel) {  
			echo $print_world[$cel];  
		}  
		echo “<br />”;  
	}  
}  
?>