Subject: RE: Generics...
MR K P SCHUPKE
k.schupke at imperial.ac.uk
Mon Feb 9 12:47:27 EST 2004
> the identity function will convert one to the other
Okay. This I understand.
I understand why the type of a generic transform has to be:
gtrans :: Data a => a -> a
and thinking about this has given me the solution. Obviously
my data types are wrong... If a loose one type and create an
angebraic type instead along the lines of:
data SqlType a = TypedExpr String | SqlColumn String
Then I can express the function I want generically.
Where this leads to messy nested constructors, I can use
constructor functions to neaten things up again.
So... I need to think about the generic transforms I wish
to implement before specifying the data types.
This will probably lead to a better use of the types anyway.
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