[Ticket #2393] Text.PrettyPrint.HughesPJ: Bug fixes, performance improvement

[Thorkil Naur]

Hello Benedikt,

Thanks for all this. From memory, notes, and (last resort) trac search, the 
HughesPJ-related trac tickets on the GHC trac are:

#669 negative indentation in Text.PrettyPrint.HughesPJ
#1176 Infinite loop when printing error message
#1217 Add zeroText to Text.PrettyPrint.HughesPJ
#1337 Fix wrong indentation from Text.PrettyPrint.HughesPJ fill (fcat and 
fsep)

I have added comments to #669 and #1176 that I hope speak for themselves. The 
problem reported in #1337 has a fix (Fix of wrong indentation from HughesPJ 
fill (fcat and fsep)), it may still provide some inspiration.

On Wednesday 25 June 2008 14:41, Benedikt Huber wrote:
> ...
> thorkil: Can you help me with a simplified test case (pretty printer 
> only) of Bug #1176 ?

#1176 is a case of #1337 for the internal GHC version of the HughesPJ library 
and I expect a fix of #1337 to be applicable to the internal GHC library, 
hence fixing #1176. So I expect the failing cases for #1337 to fail for #1176 
as well, but being, unfortunately, somewhat less easily exercised.

> Also, I didn't find any regressions tests for the pretty printer - I'll 
> create some if someone points me in the right direction.

The patch (Patch with HughesPJ tests with automated high-level coverage check) 
attached to #1337 has some tests, but also some rather bombastic things that 
attempts to ensure some coverage of the tests. This was created at a point in 
time where hpc was not available.

> ...

Thanks and best regards
Thorkil