Data commit

Task/Permutations/Modula-2/permutations.mod2

@@ -0,0 +1,60 @@
+MODULE 	Permute;
+
+FROM	Terminal
+IMPORT	Read, Write, WriteLn;
+
+FROM	Terminal2
+IMPORT	WriteString;
+
+CONST	MAXIDX = 6;
+	MINIDX = 1;
+
+TYPE	TInpCh = ['a'..'z'];
+	TChr   = SET OF TInpCh;
+
+VAR	n,
+	nl:	INTEGER;
+	ch:	CHAR;
+	a:	ARRAY[MINIDX..MAXIDX] OF CHAR;
+	kt:     TChr = TChr{'a'..'f'};
+
+PROCEDURE output;
+VAR	i:	INTEGER;
+BEGIN
+	FOR i := MINIDX TO n DO Write(a[i]) END;
+	WriteString(" | ");
+END output;
+
+PROCEDURE exchange(VAR x, y : CHAR);
+VAR	z:	CHAR;
+BEGIN z := x; x := y; y := z
+END exchange;
+
+PROCEDURE permute(k: INTEGER);
+VAR	i:	INTEGER;
+BEGIN
+	IF k = 1 THEN
+		output;
+		INC(nl);
+		IF (nl MOD 8 = 1) THEN WriteLn END;
+	ELSE
+		permute(k-1);
+		FOR i := MINIDX TO k-1 DO
+			exchange(a[i], a[k]);
+			permute(k-1);
+			exchange(a[i], a[k]);
+		END
+	END
+END permute;
+
+BEGIN
+	n := 0;	nl := 1; WriteString("Input {a,b,c,d,e,f} >");
+	REPEAT
+		Read(ch);
+		IF ch IN kt THEN INC(n); a[n] := ch; Write(ch) END
+	UNTIL (ch <= " ") OR (n > MAXIDX);
+
+	WriteLn;
+	IF n > 0 THEN permute(n) END;
+	(*Wait*)
+END Permute.