Thanks both for the the explanation and the link. The wikibook is really
growing fast!
Abhay
On Wed, May 7, 2008 at 5:05 PM, apfelmus
Abhay Parvate wrote:
Just for curiocity, is there a practically useful computation that uses 'seq' in an essential manner, i.e. apart from the efficiency reasons?
I don't think so because you can always replace seq with const id . In fact, doing so will get you "more" results, i.e. a computation that did not terminate may do so now.
In other words, we have
seq _|_ = _|_ seq x = id for x > _|_
but
(const id) _|_ = id (const id) x = id for x > _|_
So, (const id) is always more defined (">") than seq .
For more about _|_ and the semantic approximation order, see
http://en.wikibooks.org/wiki/Haskell/Denotational_semantics
Regards, apfelmus
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