Some people seem to think that == is an equality predicate.
This is a big source of confusion for them; until they realize that == is
just another function returning Bool they will make claims like [1..]==[1..]
having an unnatural result.
The == function is only vaguely related to the equality predicate in that it
is meant to be a computable approximation of semantic equality (but since
it's overloaded it can be anything, of course).
-- Lennart
On Jan 10, 2008 10:34 AM,
Achim Schneider:
jerzy.karczmarczuk asks what's wrong with:
[1..] == [1..]
Whatever you may say more, this is neither obscure nor a bug. I still wait for a relevant example. But I don't insist too much...
It's not an example of a bug, but of a cause.
A cause of WHAT?? This is a perfect, nice, runaway computation, which agrees with all dogmas of my religion.
Now, if somebody says that the fact that some people find it difficult to grasp the essence of laziness, and THIS is a source of bugs, I may believe. But not the laziness itself. (For some people the (==) operator seems to be a permanent source of bugs.)
The difference between fold and stricter fold' won't convince me either. People who want to use laziness must simply read the documentation...
On the other hand, what Don Stewart pointed out, the inconsistency between enumFrom and enumFromTo, and the difference of behaviours when one passes from Int to Integer, now, this is another story, worrying a little... Thanks.
Perhaps another example is more relevant, the tradeoffs space-time in the "optimized" version of the powerset generator...
Jerzy Karczmarczuk
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