grammar ANF;

aexp
    : IDENT #var
    | NUMBER #num
    | '(' aexp '+' aexp ')' #add
    | '(' aexp '-' aexp ')' #sub
    | '(' aexp '*' aexp ')' #mul
    | '(' aexp '/' aexp ')' #div
    | '(' IDENT ':' cexp ')' #lam
    ;

funcall
    : IDENT '(' aexp (',' aexp)* ')' #call
    | aexp #atom
    ;
cexp
    : 'let' IDENT '=' funcall 'in' cexp #let
    | funcall #fc
    ;

IDENT: Letter (Letter | Digit)*;
NUMBER: Digit+;

fragment Letter: 'A' .. 'Z' | 'a' .. 'z';
fragment Digit: '0'..'9';

WS: [ \t\n\r]+ -> skip;