[Haskell-cafe] singleton types

Günther Schmidt gue.schmidt at web.de
Sun Apr 25 17:32:01 EDT 2010

Hello Luke,

I mean something like

data FirstName = FirstName

data LastName = LastName

data BirthDate = BirthDate


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


Am 25.04.10 23:22, schrieb Luke Palmer:
> 2010/4/25 Günther Schmidt<gue.schmidt at web.de>:
>> 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

More information about the Haskell-Cafe mailing list