Hi Ben,
This is indeed a bug in parsec.
I have written a patch that fixes this. Currently Antoine Latter (current
parsec's maintainer) and I are working on getting these patches into the
next parsec release.
As a workaround until then, you can apply the attached patch manually.
darcs get http://code.haskell.org/parsec3
cd parsec3
darcs apply parsec.dpatch
cabal install
With this patch, the error message is:
Left "(unknown)" (line 18, column 1):
expecting space or atom name
* Ben Gamari
Recently I've been playing around with Parsec for a simple parsing project. While I was able to quickly construct my grammar (simplified version attached), getting it working has been a bit tricky. In particular, I am now stuck trying to figure out why Parsec is mis-reporting line numbers. Parsec seems convinced that line 12 of my input (also attached) has a "%" character,
$ runghc Test.hs Left "(unknown)" (line 12, column 1): unexpected "%" expecting space or atom name
while my file clearly disagrees,
10 %FLAG ATOM_NAME 11 %FORMAT(20a4) 12 C1 H1 C2 H2 C3 H3 C4 H4 C5 C6 C7 C8 N1 C9 H9 C10 H10 C11 H11 C12 13 H12 C13 H13 C14 C15 N2 C16 C17 C29 H18 C19 H19 C20 H20 C21 H21 C22 H221H222H223 ... 18 %FLAG CHARGE 19 %FORMAT(5E16.8)
The task here is to identify the block of data lines (lines 12-17), ending at the beginning of the next block (starting with "%"). It seems likely that my problem stems from the fact that I use "try" to accomplish this but this is as far as I can reason.
Any ideas what might cause this sort of off-by-one? Does anyone see a better (i.e. working) way to formulate my grammar? Any and all help would be greatly appreciated. Thanks.
Cheers,
- Ben
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