[web-devel] yesod IRC meeting summary

[Greg Weber]

# Groundhog

We discussed Persistent and Groundhog with Boris, the author of Groundhog
who was kind enough to show up and meet with us.

The differences were summarized:
* groundhog uses gadts to greatly clean up PersistEntity, and to avoid the
need for a bunch of associated types and extra constructors. downside: gadts
+ type families is a ghc 7 feature, although it might be possible to use
phantom types and support ghc6
* persistent requires all datatypes be defines through its QQ syntax,
groundhog allows types to be declared as normal. i think this allows
persistent to sidestep a lot of sticky naming issues, but groundhog is more
flexible
* groundhog supports "and" and "or", persistent only supports "and
* groundhog use operators, persistent uses constructors
* groundhog supports complex arithmetic expressions
* groundhog supports comparing fields to fields