[antlr-interest] Simple lexical predicate question
ryan.hollom at us.lawson.com
Tue Sep 12 07:27:22 PDT 2006
I am writing a parser/lexer for a language with the following constructs,
and am having difficulty getting the lexer to work properly.
identifier is a Field
identifier is a LocalField
identifier is Numeric
identifier is an AddressField
So, I have the keywords 'is a Field', 'is a', 'is', and 'is an'
('LocalField' and 'AddressField' can be any name, and 'Numeric' can be one
of about 30 different things).
I've had a difficult time defining the rules for these, as I get a lexer
no viable alt error. Here is an example of my rule:
identifier 'is a Field'
(('is a' | 'is an') identifier) | 'is'
primitiveType : 'Alpha' | 'Numeric';
The lexer then chokes on input like:
MyField is a Field
MyNumericField is Numeric
with a no viable alt line 2:20; char='N'
I assume that I need to define lexer rules for the 'is ...' keywords with
some type of predicate, but haven't been able to figure it out yet. Could
someone point me in the right direction?
Thanks in advance,
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