[Haskell-cafe] conflicting variable definitions in pattern

[Miguel Mitrofanov]

What would you expect

foo [id, \x -> x]

to be?

Martin Hofmann wrote on 15.05.2009 12:09:
> It is pretty clear, that the following is not a valid Haskell pattern:
> 
> foo (x:x:xs) = x:xs
> 
> My questions is _why_ this is not allowed. IMHO, the semantics should be
> clear: The pattern is expected to succeed, iff 'x' is each time bound to
> the same term. 
> 
> Isn't this allowed, because this would require a strict evaluation of
> the 'x' variables?
> 
> Thanks,
> 
> Martin
> 
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