best way to memoize a range?
Laeeth Isharc via Digitalmars-d-learn
digitalmars-d-learn at puremagic.com
Fri Sep 11 14:47:30 PDT 2015
On Friday, 11 September 2015 at 13:31:06 UTC, John Colvin wrote:
> On Friday, 11 September 2015 at 13:09:33 UTC, Laeeth Isharc
> wrote:
>> obviously it's trivial to do with a little aa cache. and I
>> know I can memoize a function, and turn the memoized version
>> into an infinite range. but suppose I have a lazy function
>> that returns a finite range, and its expensive to calculate.
>>
>> can I use Phobos to produce a memoized range? So it will
>> calculate on access to an element if it needs to, but will
>> return the cached value if it has been calculated before.
>
> perhaps
> http://dlang.org/phobos/std_algorithm_iteration.html#.cache
> would do what you need. An AA based cache (with a normal range
> interface if you want) is probably the sensible way to get true
> random-access here, unless you have reasonably dense and
> monotonic accesses in which case an appender-based linear cache
> could work, either using Nullable!T or a separate list of bools
> (or bits) marking whether a result is cached yet.
Thanks, John and Jacob.
Laeeth.
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