On Tue, Dec 04, 2007 at 03:07:01PM -0800, Ryan Ingram wrote: > Is there a reason why strictness is defined as > > f _|_ = _|_ > > instead of, for example, > > forall x :: Exception. f (throw x) = throw x > where an exception thrown from pure code is observable in IO. > > In the second case we need to prove that the argument is evaluated at some > point, which is also equivalent to the halting problem but more captures the > notion of "f evaluates its argument" rather than "either f evaluates its > argument, or f _ is _|_" > > I suppose the first case allows us to do more eager evaluation; but are > there a lot of cases where that matters?
"Is there a reason why 2 + 2 is defined as 4 instead of, for example, 5?" Strictness is more useful in practice, simpler to define, and easier to approximate. What benefit does your notion offer? Stefan
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