On Jul 9, 2007, at 6:52 PM, Donald Bruce Stewart wrote:
bayer:
Learning Haskell, the Prelude.ShowS type stood out as odd, exploiting
the implementation of lazy evaluation to avoid explicitly writing an
efficient concatenable list data structure.
See also
http://hackage.haskell.org/cgi-bin/hackage-scripts/package/
dlist-0.3
Thanks; I added a link to the dlist package from my discussion of
this idiom on the Wiki page
http://www.haskell.org/haskellwiki/Prime_numbers
On Jul 9, 2007, at 3:19 PM, Jonathan Cast wrote:
I think we usually call it `exploiting laziness'. . .
My motivation in asking for a name was to be able to find other
Haskell one-liners adequately replacing chapters of data structure
books for problems of modest scale, e.g. finding the 5,000,000th
prime. So far, I know concatenable lists, and heaps. Is there a Wiki
page where someone teaches this principle for a dozen other classic
data structures? Your "one-liner" made me laugh, but it didn't help
me in googling, I would have preferred a one-liner teaching me
another classic data structure, or an explanation of why burrowing
into the GHC implementation gives such a speed advantage over a
carefully written explicit data structure.
People in other camps don't really "get" lazy evaluation, even many
of our ML neighbors. It would pay to communicate this better to the
outside world.
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