mwinter@brocku.ca wrote:
Hi,
I am using parsec to parse a small programming language. The language is typed and I need to do some type checking, too. I have decided to do the parsing and type checking simultaneously in the my parsec parser. This approach avoids to keep source code positions in the data type in order to produce suitable error messages during type checking. Anyhow, because type errors are usually detected after parsing some code I need produce error messages with an earlier source position. Unfortunately, there is no function that produces an error taking a position as parameter.
If you already know what position you want to report the error at, then why bother calling setPosition to let parsec know? Just do:
fail (show pos ++ ": " ++ msg)
Parsec will then result in a ParseError with its own ideas of location, but you can ignore that. HTH, Martijn.