Question

I have a grammar defined roughly like this.

TOKEN:{
        <T_INT: "int"> |
        <T_STRING: ["a"-"z"](["a"-"z"])*>
}

SKIP: { " " | "\t" | "\n" | "\r" }

/** Main production. */
SimpleNode Start() : {}
{
        (LOOKAHEAD(Declaration()) Declaration() | Function())
  { return jjtThis; }
}

void Declaration() #Decl: {}
{
        <T_INT> <T_STRING> ";"
}

void Function() #Func: {}
{
        <T_STRING> "();"
}

This works fine for stuff like:

int a;
foo();

But when I try int();, which is legal for me and should be parsed by the Function(), it goes for the Declaration instead. How do I fix this “conflict”? I tried various combinations.

Answer 1

The JavaCC FAQ’s section on this is titled “How do I deal with keywords that aren’t reserved?”.

What I would do is allowing the keywords alternatively to the identifiers, i.e.

(<T_STRING> | <T_INT>) "();"

When there are many keywords, it could be beneficial to create an Identifier production that allows them all, along with the general identifier token.

By the way, you might want "(" ")" ";" instead of "();".