Gentle Haskellers,
Here's a Haskell98-typo question.
Consider this program:
module M where
reverse xs = Prelude.reverse (tail xs)
foo ys = M.reverse ys
This is legal Haskell98. The call to Prelude.reverse and to M.reverse
must both be qualified, because plain 'reverse' would be ambiguous.
But the definition of reverse does not need to be qualified, becuase it's
a definition!
Now, would it be legal to add this type signature to the end of M?
reverse :: [a] -> [a]
Or should it be
M.reverse :: [a] -> [a]
I can see two arguments
A) The unqualified form should be legal because the type signature
can only refer to the 'reverse' defined in this module
B) The unqualified form is ambiguous. All occurrences of 'reverse',
other than the definition itself, must be qualified
The Report itself does not answer the question clearly,
so I propose to resolve the ambiguity.
Personally I'm inclined to resolve it in favour of (B). In due course we
may want to allow type signatures for imported things in a module, for
example. Does anyone object?
Simon
