grammar ANF;

aexp
    : IDENT
    | NUMBER
    | aexp '+' aexp
    | aexp '-' aexp
    | aexp '*' aexp
    | aexp '/' aexp
    | '(' IDENT ':' cexp ')'
    ;

funcall
    : IDENT '(' aexp (',' aexp)* ')'
    | aexp
    ;
cexp
    : 'let' IDENT '=' funcall 'in' cexp
    | funcall
    ;

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

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

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