INTERFACE Arg;

TYPE
  T = REF RECORD
    arg: TEXT;
    next: T;
  END;

TYPE
  List = REF RECORD
    head, tail: T := NIL;
    cnt := 0;
  END;

PROCEDURE NewList (): List;

return [ ]

PROCEDURE Append (list: List;  val: TEXT);

list := [ list val ]

PROCEDURE Prepend (list: List;  val: TEXT);

list := [ val list ]

PROCEDURE AppendL (a, b: List);

a := [ a b ]

PROCEDURE Pop (list: List): TEXT;

list = [ a b ] => list := [ b ]; return a

PROCEDURE Flatten (list: List;  other: TEXT): REF ARRAY OF TEXT;

return an array of text equal to Append (list, other)

END Arg.