program ExpressionEval;

{$APPTYPE CONSOLE}

uses
  SysUtils;

type
    Identifier = record
    Name : String;
    Value : String;
end;

const CAPACITY = 19;

var
  menuchoice : char;
  i : integer;
  identValue : String;
  identName : String;
  identArray : array[0..CAPACITY] of Identifier;
  arrayCounter : integer;

procedure menu;
begin
  arrayCounter := 0; {array counter initialisation}
  writeln ('(d)isplay menu');
  writeln ('(l)ex keyboard input to tokens');
  writeln ('(p)arse the tokens into a parse tree');
  writeln ('(e)valuate the parse tree');
  writeln ('(b)ind an identifier to a value');
  writeln ('(s)how the values of all the identifiers');
  writeln ('(q)uit');
  writeln;
  write ('Selection => ');
  readln (menuchoice);

  case menuchoice of
    'd': menu {re-displays the menu};
    'l': {lex into tokens};
    'p': {parse tokens into tree};
    'e': {evaluate tree};
    'b': {Get user-entered values for identifiers}
          begin
            write ('Enter the name of the identifier : ');
            readln (identName);
            identArray[arrayCounter].Name := identName;

            write ('Enter the value to assign to this identifier : ');
            readln (identValue);
            identArray[arrayCounter].Value := identValue;

            writeln ('Identifier added');
            arrayCounter := arrayCounter + 1;
            writeln;
            menu;
          end;
    's': {display all identifiers}
          begin
            for i := 0 to arrayCounter do
            begin
              writeln ((identArray[i].Name), ' : ', (identArray[i].Value));
            end;
            writeln ('End of list');
            writeln;
            menu;
          end;
    'q': {nothing - quits program};

    else
      writeln ('Invalid selection, please choose again');
      menu;
  end;
end;

begin
  menu;
end.