token Constructor (["ABCDEFGHIJKLMNOPQRSTUVWXYZ"]
                   (["abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-'"]
                   | digit
                   )*);
token Variable    (["abcdefghijklmnopqrstuvwxyz_"]
                   (["abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-'"]
                   | digit
                   )*);

Apply  . Exp1 ::= Exp1 Exp2;
Lambda . Exp  ::= "\\" Variable "." Exp;
Case   . Exp1 ::= "case" Exp "of" "{" [Br] "}";
Rec    . Exp  ::= "rec" Variable "=" Exp;
Var    . Exp2 ::= Variable;
Const  . Exp2 ::= Constructor "(" [Exp] ")";
_      . Exp  ::= Exp1;
_      . Exp1 ::= Exp2;
_      . Exp2 ::= "(" Exp ")";

Branch . Br ::= Constructor "(" [Variable] ")" "->" Exp;

separator Br       ";";
separator Exp      ",";
separator Variable ",";

comment "--";
comment "{-" "-}";