On 15/09/2011 23:58, Ian Lynagh wrote:
The next 2 patches (for base and unix respectively) remove the Eq constraint. Here's there's some justification in the superclass, as it makes f 5 = ... work for any Num type, rather than also needing an Eq constraint, but personally I would be in favour of removing this superclass too. Noteworthy is that Bits now needs an Eq superclass for the default methods for 'testBit' and 'popCount'.
I have a vague recollection that there are some generic implementations of sqrt that rely on equality tests with 0. I can't spot any in the Haskell library source, though. Otherwise +1; one significant benefit of this change would be for EDSLs which currently have to have broken Eq instances to implement Num. Cheers, Ganesh