[Haskell-cafe] Re: Why purely in haskell?
Tillmann Rendel
rendel at rbg.informatik.tu-darmstadt.de
Thu Jan 10 18:05:42 EST 2008
Achim Schneider wrote:
> [1..] == [1..]
>
> [some discussion about the nontermination of this expression]
>
> The essence of laziness is to do the least work necessary to cause the
> desired effect, which is to see that the set of natural numbers equals
> the set of natural numbers, which, axiomatically, is always
> computable in O(1) by equality by identity.
This would make sense if Haskell had inbuild equality and (==) where
part of the formal semantics of Haskell, wich it isn't. (==) is a
library function like every other library function. How could the
language or a system implementing the language decide wether this or any
other library function returns True without actually running it?
Haskell is a programming language, not a theorem prover.
Tillmann
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