Data.Sequence actually doesn't support anything outside the Int range. It
could, at a small cost. We perform some range checks cheaply using unsigned
comparisons. We'd have to stop doing that to allow sequences to be just a
tad more absurdly large. Since that's not often useful, sequences are
currently limited to lengths of maxBound @Int.
On Thu, Nov 15, 2018, 5:53 PM Zemyla It's not actually impossible to have an in RAM structure that exceeds
the largest positive value for Int. Data.Sequence.replicate does it by
exploiting sharing. replicate n a uses O(lg n) space. length $ let x = Data.Sequence.Replicate maxBound 'a' :> 'b' in mappend
x x
0 Also, I really would like to have all the length and count-based
functions in base, containers, etc. take or return Words, but there's
way too much inertia behind Ints, even if it means you have to check
for negative numbers (which really runs counter to the main thesis
behind Haskell; i.e. have your types say what you mean). On Thu, Nov 15, 2018 at 12:30 AM Carter Schonwald
Agreed. As David and Eric both say:
For in heap / memory size structures, it’s impossible to ever have an in ram structure that exceeds the largest positive value for Int. And ghc is
also quite good at optimizing int. 1) what is your application domain / context ? 2) all of these are implementable in user space, what design / implementation experiments have you done ? It’s worth mentioning that RULES style optimization in this case would only run AFTER it’s been specialized to a concrete type. And that short of
lots of specialize pragmas or inlining , the generic code will thusly miss
out on all sorts of unboxong etc. On Tue, Nov 13, 2018 at 10:31 PM David Feuer That won't help whatsoever in most cases. The matter has been discussed several times with no progress. If you want to add RULES for Int8, Int16,
..., Word, Word8, ..., and Natural to match the ones for Int and Integer, On Tue, Nov 13, 2018, 10:24 PM Vanessa McHale wrote: This is perhaps not the right place, but if there are benchmarks wrote:
that would make sense, but the basic problem will remain for unmentioned
types.
proving that genericLength is slower than it should be, it should be easy
to add a SPECIALIZE pragma. On 11/13/18 9:13 PM, David Feuer wrote: genericLength is extremely inefficient for typical numeric types. Int is a rather sad type for these things; it really should be Word. But that
may not be worth fixing. On Tue, Nov 13, 2018, 9:51 PM Evan Laforge You can already get these as Data.List.genericLength and
Data.List.genericReplicate As for changing the prelude ones, this would probably cause a lot of
busywork. Where I work we compile with -Werror and -Wtype-defaults,
so a lot of places might have to get type annotations.
On Tue, Nov 13, 2018 at 5:19 PM Vanessa McHale < vanessa.mchale@iohk.io> wrote: Would it be possible to generalize replicate and length to have type
signatures replicate :: Integral a => a -> b -> [b] and length :: (Integral a, Foldable t) => t b -> a ? There have been a few instances where such a thing would have been
useful to me. Cheers _______________________________________________
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