The states generated by Alex are a bit inflexible, you could modify the (user) state when dealing with nested comments I think but then checking state before applying a rule might be expensive. Cheers, Vanessa McHale On 2/9/21 10:57 PM, Benjamin Redelings wrote:
Hi,
I notice that in Lexer.x for GHC nested comments are parsed using a special function, with the comment "nested comments require traversing by hand, they can't be parsed using regular expressions."
While I see that nested comments can't be parsed using regular expressions, the lexer has a state stack, and so it seems like nested comments could be parsed by pushing a new "nested comment" state onto the lexer state every time a "{-" is encountered. But perhaps this is not done because its not clear how to make the entire comment into a single token that way? This might be a naive question -- I don't have that much experience with lexers.
Thanks!
-BenRI
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