In the original language design the Haskell committee considered
allowing multiple occurrences of the same variable in a pattern (with
the suggested equality tests), but it was rejected in favour of
simplicity.
-- Lennart
On Fri, May 15, 2009 at 11:30 AM, Sittampalam, Ganesh
Conor McBride wrote:
On 15 May 2009, at 09:11, Sittampalam, Ganesh wrote:
but then pattern matching can introduce Eq constraints which some might see as a bit odd.
Doesn't seem that odd to me. Plenty of other language features come with constraints attached.
It's the introduction of a constraint from tweaking a pattern that is odd, I think. By way of precedent H98 rejected this kind of idea in favour of putting 'fail' into Monad.
Ganesh
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