12 Nov
2004
12 Nov
'04
12:45 p.m.
Marcin 'Qrczak' Kowalczyk wrote:
oleg@pobox.com writes:
Thus we have reduced the problem of excluding certain types from a typeclass to the problem of excluding all types from one particular typeclass: Fail. How can we prevent the user from adding instances to Fail?
By not exporting its name?
Perhaps that should have read: How can we prevent the user from adding instances to Fail, whilst still exporting Fail so that it can be used in the constraints of other classes, like: class MustBeInt a instance MustBeInt a instance Fail a => MustBeInt a Keean.