(forgot to CC the list) On Jun 24, 2011, at 8:27 PM, Daniel Patterson wrote:
> It looks, from looking at the provided instances (not from having done it > myself), that you need to define safeConvert functions to and from your > value. Here is a partial list of conversions to and from String. > instance Convertible String SqlValue where > safeConvert = return . SqlString > instance Convertible SqlValue String where > safeConvert (SqlString x) = return x > safeConvert (SqlByteString x) = return . BUTF8.toString $ x > safeConvert (SqlInt32 x) = return . show $ x > safeConvert (SqlInt64 x) = return . show $ x > safeConvert (SqlWord32 x) = return . show $ x > safeConvert (SqlWord64 x) = return . show $ x > safeConvert (SqlInteger x) = return . show $ x > safeConvert (SqlChar x) = return [x] > safeConvert (SqlBool x) = return . show $ x > safeConvert (SqlDouble x) = return . show $ x > safeConvert (SqlRational x) = return . show $ x > > On Jun 24, 2011, at 8:02 PM, Tom Murphy wrote: > >> Hi *, >> The title is self-explanatory. I'd like to store information from >> an algebraic data type in an SQL database, but the type signature of >> toSql (toSql >> :: Data.Convertible.Base.Convertible a SqlValue => a -> SqlValue) >> doesn't make sense to me. >> How is this done (how do I make an instance of a typeclass like that?) >> >> Thanks for your time, >> Tom >> >> _______________________________________________ >> Haskell-Cafe mailing list >> [email protected] >> http://www.haskell.org/mailman/listinfo/haskell-cafe >
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