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.