You could add {-# LANGUAGE DeriveFunctor #-}, and then add 'deriving
Functor' to all your data types (or you could of course manually
define your functor instances). Then what you want is just 'fmap
show'.
Erik
On Tue, Oct 2, 2012 at 9:55 AM, Sergey Mironov
Hi! I have a syntax tree defined like this:
data A a = A Int Int (B a)
data B a = B String String (C a)
data C a = C Int Int (D a)
and so on, all the data are parametrized with a type variable. This variable is actually used as a field in the very end of a hierarchy:
data D a = D Int a
Now I have to write a function which would copy (A Int) to (A String). Is it possible to do so using TH/syb without writing
copyA (A i1 i2 b) = A i1 i2 (copyB b) copyB = ... copyC = ... .. copyD (D i a) = D i (show a) ?
Could you provide me with a hint?
Thanks, Sergey
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