Mark T.B. Carroll wrote:
Bryan O'Sullivan <[EMAIL PROTECTED]> writes:
Mark T.B. Carroll wrote:
I'm afraid no
examples come easily to mind, though.
Here's a simple one: reading a flattened graph from disk. If your
flattened representation contains forward references, you have to fix
them up in a strict language. In a lazy language, you can refer to
elements you haven't yet read, eliminating that book-keeping.
That's a good point. Indeed, I had used laziness in a programme that
read a file that contained a series of entity definitions that could
include forward references, I just couldn't remember exactly how I'd
used laziness. (-: (It's also useful in some memoising, I think.)
-- Mark
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Near the bottom of http://www.haskell.org/hawiki/TyingTheKnot is an example that
uses lazy evaluation to do exactly this. The real kicker though, is that the
change from backward references only (i.e. simplistic one-pass code that would
work in a strict language) to forward and backward references is trivial (just
pass in the output).
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