JavaCC: How can I specify which token(s) are expected in certain context?
- by java.is.for.desktop
Hello, everyone!
I need to make JavaCC aware of a context (current parent token), and depending on that context, expect different token(s) to occur.
Consider the following pseudo-code:
TOKEN <abc> { "abc*" } // recognizes "abc", "abcd", "abcde", ...
TOKEN <abcd> { "abcd*" } // recognizes "abcd", "abcde", "abcdef", ...
TOKEN <element1> { "element1" "[" expectOnly(<abc>) "]" }
TOKEN <element2> { "element2" "[" expectOnly(<abcd>) "]" }
...
So when the generated parser is "inside" a token named "element1" and it encounter "abcdef" it recognizes it as <abc>, but when its "inside" a token named "element2" it recognizes the same string as <abcd>.
element1 [ abcdef ] // aha! it can only be <abc>
element2 [ abcdef ] // aha! it can only be <abcd>
If I'm not wrong, it would behave similar to more complex DTD definitions of an XML file.
So, how can one specify, in which "context" which token(s) are valid/expected?
NOTE: It would be not enough for my real case to define a kind of "hierarchy" of tokens, so that "abcdef" is always first matched against <abcd> and than <abc>. I really need context-aware tokens.
