[Haskell-cafe] Preventing sharing
oleg at okmij.org
Mon Dec 21 11:55:05 UTC 2015
> -fno-full-laziness fixes the space leak issue in your iterative deepening
Yes, and I think it has been mentioned that the flag is a blunt weapon
as it affects the whole module...
> This isn't a problem with laziness. It's a problem with performing a time
> optimization which is a space pessimization. In the absence of the
> "optimization" there is no problem.
How come it isn't the problem with laziness?! Recall, that pure
call-by-name calculus is observationally undistinguishable from the
call-by-need (i.e., lazy) calculus. The only reason to have laziness
is to avoid recomputations of argument computations should an argument
be used more than once -- at the cost of taking memory to store the
result of the first evaluation. Thus "performing a time optimization
which is a space pessimization" is exactly what laziness is all about
-- as the article mentioned earlier argued. Laziness isn't an absolute
good -- it is a time-space trade-off, which is not always beneficial.
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