[Haskell-cafe] Re: Control.Exception.evaluate - 'correct
definition' not so correct
apfelmus at quantentunnel.de
Wed May 7 07:35:40 EDT 2008
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 > _|_
(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
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