Ketil Z. Malde
02 Oct 2002 13:20:55 +0200
At the moment, I have a user defined data type on which I have defined
some operations, instantiated (not derived) Eq and so on. However,
for efficiency I'm storing the actual data in UArrays of Word8.
In order for everything to work, I need functions 'toW8' and 'fromW8'
to map between the data type and its representation in the array.
I gather it is impossible to hide the 'Eq' instance of Word8 and/or
redefine it, but could this be circumvented by instead of
data Foo = F | G
instance Eq Foo where
F == _ = True
_ == _ = False
defining something like
newtype Foo = F Word8
f, g, h :: Foo
f = F 0
g = F 1
and using the same instance declaration? And will it still fit into a
(It is of course possible that, while profiling indicates otherwise,
the conversion functions have little impact in practice; i.e. the
optimizer will do away with them.)
If I haven't seen further, it is by standing in the footprints of giants