[antlr-interest] help on warning:nondeterminism upon

[Martin Probst]

> I am getting the " warning:nondeterminism upon "
> in the line no 244,it corresponds to
>
> "createPolicy throws ArchiveSystemApplicationException
> 	    :
> CREATE WS POLICY ( WS createPolicyParams)* ( WS createPolicyTypes)*
> NEWLINE

Well, the easiest way to solve those errors is - from my experience - to
just imagine you would be the parser and had to choose which way to take.

In this case, imagine you would be after the policy statement. Now the
next token you see in lookahead is a WS token. Both ways, the way to
createPolicyParams and the way to the Types start with a whitespace. So
you can't decide which way to go.

There are several possible solutions. One of them (the possibly easiest)
is to ignore whitespaces within the lexer so the parser doesn't have to
care about them:
WS: (your whitespace characters)* { $setType(Token.SKIP); }

Alternatively - if you need whitespaces - you might do this:
CREATE WS POLICY ( ( WS createPolicyParams ) => WS createPolicyParams )*
  ( ( WS createPolicyTypes ) => WS createPolicyTypes )*
This solution is worse as it takes some overhead to do the lookahead in
the rule.

There are more solutions to this, but I would recommend to you to check
whether you can ignore whitespaces. You can always control whitespace
ignoring via a boolean flag within the lexer which can be set in certain
situations (I do that within my grammar):
WS: (...) { if (wsIgnorable) $setType(Token.SKIP); }

mfg
Martin


 
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