RosettaCodeData/Task/Menu/Modula-2/menu.mod2

MODULE  Menu;

FROM    InOut IMPORT WriteString, WriteCard, WriteLn, ReadCard;
FROM    STextIO IMPORT ReadChar, SkipLine;
FROM    CharClass IMPORT IsNumeric, IsControl, IsWhiteSpace;

CONST   StringLength     = 100;
        MenuSize         = 4;

TYPE    String           = ARRAY[0..StringLength-1] OF CHAR;

PROCEDURE MenuF(): String;
VAR
    menu             : ARRAY[0..MenuSize] OF String;
    inp              : CHAR;
    selection, index : CARDINAL;

BEGIN
    menu[1] := "fee fie";
    menu[2] := "huff and puff";
    menu[3] := "mirror mirror";
    menu[4] := "tick tock";
    selection := 0;
    WHILE selection=0 DO
        FOR index := 1 TO HIGH(menu) DO
            WriteString("[");
            WriteCard(    index,1);
            WriteString(        "] ");
            WriteString(            menu[index]);
            WriteLn;
        END;(*of FOR*)

        inp := '';
        WriteString("Choose what you want : ");
        ReadChar(inp);
        SkipLine;

        IF IsNumeric(inp) THEN
            CASE inp OF
               '1' : selection := 1 |
               '2' : selection := 2 |
               '3' : selection := 3 |
               '4' : selection := 4 |
            ELSE ;
                selection := 0;
            END;

            IF (selection <= HIGH(menu)) AND (selection > 0) THEN
                RETURN menu[selection];
            END (*of IF*)
        ELSIF IsWhiteSpace(inp) OR IsControl(inp) THEN
            RETURN "";
        END;
    END;
END MenuF;

BEGIN
    WriteString(MenuF());
    WriteLn;
END Menu.