[Haskell-cafe] advanced class constraints in Haskell 98?
lemming at henning-thielemann.de
Thu Jan 8 19:11:12 EST 2009
On Fri, 9 Jan 2009, Miguel Mitrofanov wrote:
> On 9 Jan 2009, at 02:47, Ross Paterson wrote:
>> On Thu, Jan 08, 2009 at 10:27:59PM +0100, Henning Thielemann wrote:
>>> A nice. I jumped into 4.3 and found
>>> scontext -> simpleclass
>>> | (simpleclass_1, ..., simpleclass_n)
>>> simpleclass -> qtycls tyvar
>>> So it must be 'atype' instead of 'tyvar'? Haskell 98 is really mighty.
>> Oh. Don't I look silly? You were absolutely right, it's not Haskell 98.
> Me too. I've looked at the type declaration syntax instead of instance
> declaration one.
Maybe the report is not complete? I mean, the current behaviour of Hugs
and GHC (as I observed it) is more consistent, and maybe that's what the
designers had in mind.
>> Actually Hugs does reject it without flags. Maybe you have a -98 stored
When starting, my Hugs tells
Haskell 98 mode: Restart with command line option -98 to enable extensions
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