On 18/07/10 22:59, Ian Lynagh wrote:
Hi all,
H98 and H2010 allow a context to be given for datatypes, e.g. the "Eq a" in
data Eq a => Foo a = Constr a
I have made a proposal to remove support for that context (ticket #139). More details are on the proposal wiki page:
http://hackage.haskell.org/trac/haskell-prime/wiki/NoDatatypeContexts
To provide a data point: I was surprised to see CHP on the list of packages that didn't compile without data-type contexts, as I didn't realise I was using them. I found one in a source file I haven't touched for a while, and removing it made no difference -- the library compiled fine. I'm all for the proposal -- it stops people (like me!) inadvisedly using datatype contexts despite them not actually doing anything. Thanks, Neil.