Hi Tobias, Hi All,

On Tue, Oct 25, 2016 at 1:03 PM, Tobias Pape <Das.Linux at gmx.de> wrote:

>
> On 25.10.2016, at 21:45, Chris Muller <asqueaker at gmail.com> wrote:
>
> > Folks there is NO BASIS at the level of Collection for assuming that
> > do: [ : each | ^
> > false ] is faster than ^self size=0.  In fact, the proper assumption
> > is the opposite -- that #size is the optimized method, not #do:.
>
> I don't understand on what _either_ performance-assumption is grounded.
> Since I've apparently not been around since the early years of either
> ST-80 or Squeak, can someone enlighten me here?
>
> Both ways seem somewhat reasonable:
>  `self size = 0` is simple, easy to understand on first sight and said
> here to be more expensive than

 `self do: [:ea |  ^false]`, which is clever[1], possibly needs a
> double-take (or comment), but has a certain appeal of wholeness[2].
>

self size = 0 doesn't work for infinite collections.  The suggested
implementation of isEmpty does indeed require a comment (I didn't implement
it) but it does work for infinite collections. The suggested implementation
os isEmpty is also faster than elf size = 0 for any collection of
sufficient size.

For example:

| b n |
b := Bag someInstance.
n := 100000.
{ b size. [1 to: n do: [:ign| b isEmptyOId]] timeToRun. [1 to: n do: [:ign|
b isEmpty]] timeToRun } #(20402 3293 21)

and the cut off is quite low:


| n |
n := 10000.
((1 to: 10) collect:
[:iguana|
(1 to: SmallInteger maxVal) detect:
[:i|
b := (1 to: i) asBag.
[1 to: n do: [:ign| b isEmptyOId]] timeToRun > [1 to: n do: [:ign| b
isEmpty]] timeToRun]]) average asFloat 4.9

So for collections that are 5 elements or more the "clever" implementation
is faster.

Best regards
>         -Tobias
>
> [1]: sadly, cleverness in software typically is a drawback.
> [2]: I mean, the minimalism that is possible by just using/providing #do:
> somehow conveys closure/completeness
>


_,,,^..^,,,_
best, Eliot
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