でかいXを出力する

SML 30分プログラム

30分プログラム、その756。
anarchy golf - Xにインスパイアされて、でっかいXを出力してみました。

使い方

- print (x 3);
x     x
 x   x
  x x
   x
  x x
 x   x
x     xval it = () : unit

ソースコード

open String;

fun repeat _ 0 = []
  | repeat c n = List.tabulate (n, (fn _ => c));

fun make_string c n =
    String.implode (repeat c n);

fun range from to =
    if from = to then
	[]
    else
	from :: range (from + 1) to;

fun row n =
    let
	val m   = 2 * n + 1
	val mid = make_string #" " m
    in
	"x" ^ mid ^ "x"
    end;

fun padding width str =
    let
	val n   = (width - String.size str) div 2
	val pad = make_string #" " n
    in
	pad ^ str ^  pad
    end;

fun x n =
    let
	val downside = List.map row (range 0 n)
	val upside   = List.rev downside
	val width    = 2 * n + 1
	val big_x    = List.map (padding width) (upside @ [ "x" ] @ downside)
    in
	String.concatWith "\n" big_x
    end;

参考