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.

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