Hello Henry,
The paper A Lightweight Approach To Datatype-Generic Rewriting [1]
describes a way to generically add a constructor to any regular datatype
using type-indexed datatypes [2]. A similar technique could be used to add a
new field to each constructor. Then you get something like:
data
Dear Group,
It seems to me this should be easy, but I can't quite figure out
how to do it without a lot of typing. Here is the question:
Suppose you have a data type like:
Data Foo = Foo { a :: Int, b :: Int,
... many other fields ...
y :: Int } deriving (Eq, Read, Show, Typeable, Data)
and perhaps use emacs to
query-replace all the Foo1's back to Foo's
At least this bit can be avoided easily enough, by using
module qualification during the conversion process.
module Original (Foo(..)) where
data Foo = Foo { ... y :: Int } deriving ...
module New (Foo(..)) where
