Hello Luke, I mean something like data FirstName = FirstName data LastName = LastName data BirthDate = BirthDate ie. data FirstName data LastName data BirthDate In HaskellDB's case this is part of what's necessary to define individual columns. Another part is: instance FieldTag FirstName where fieldName = const "firstName" HaskellDB is using type level stuff quite heavily and since you're a bit of a wizkid on avoiding it where not necessary and keeping things "functional" I'm hoping you might come up with something. :) Best regards Günther Am 25.04.10 23:22, schrieb Luke Palmer:

2010/4/25 Günther Schmidt:

...

Hello,

HaskellDB makes extensive use of Singleton Types, both in its original version and the more recent one where it's using HList instead of the legacy implementation.

I wonder if it is possible, not considering feasibility for the moment, to implement HaskellDB *without* using Singleton Types.

Would you please define "singleton type"?

Luke