Martin Hofmann wrote:
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?
One reason is:
What if the list were a list of functions? How would you decide
"sameness" of lambda-terms? By investigating their in-memory
representations? By trying to prove that they denote the same
mathematical function?
Ciao, Janis.
--
Dr. Janis Voigtlaender
http://wwwtcs.inf.tu-dresden.de/~voigt/
mailto:vo...@tcs.inf.tu-dresden.de
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
