On Sun, Dec 4, 2011 at 1:05 PM, Eero Saynatkari = <ruby-ml@kit= tensoft.org> wrote:

On 2011-12-04, at 16:15:00, Alexey Muranov wrote:
>
> But what is wrong with having one class instead of two, if internally = they behave mostly the same, and one literal notation instead of two? Anywa= y, this was just an idea.

Hash tables aren't Sets, nor the other way around. I'd like t= o avoid messing up data structure definitions any more than they already ar= e.

The only compelling reason for bringing Set into core would be a literal sy= ntax =E2=80=93 and I agree, as a data structure it would be a useful additi= on and encourage its usage =E2=80=93 but I don't really have anything t= o contribute to the particular bikeshed of syntax thereof.

Actually, the bulk of Set's functional= ity is already built on top of Hash. Personally, since the ability to creat= e Hashes from comma-delimited key,value lists has been removed in 1.9, I th= ink reintroducing it to create Set literals is not the worst idea in the wo= rld.

Additionally, implementing Set functionality directly o= n top of Hash would remove the unfortunate method call overhead that curren= tly exists in the Set library (note that the implementation of Set#include?= is just a call through to Hash#include?):

>> Benchmark.bmbm do |x|

?> =C2= =A0 h =3D {}

>> =C2=A0 s =3D Set.new

>> =C2= =A0 10000.times { |i| h[i] =3D nil; s << i }

>> =C2= =A0 x.report("Hash#include?") { 1000000.times { h.include? rand(2= 0000) } }

>> =C2=A0 x.report("Set#include?") { 1000000.times { s= .include? rand(20000) } }

>> end

Rehearsal ------= -------------------------------------------

Hash#include? =C2=A0 = 0.370000 =C2=A0 0.000000 =C2=A0 0.370000 ( =C2=A00.370516)

Set#include? =C2=A0 =C2=A00.440000 =C2=A0 0.000000 =C2=A0 0.440000 ( = =C2=A00.436806)

---------------------------------------- total: 0= .810000sec

=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 user =C2=A0 =C2=A0 system =C2=A0 =C2=A0 =C2= =A0total =C2=A0 =C2=A0 =C2=A0 =C2=A0real

Hash#include? =C2=A0 0.370000 =C2=A0 0.000000 =C2=A0 0.370000 ( =C2=A0= 0.361795)

Set#include? =C2=A0 =C2=A00.430000 =C2=A0 0.000000 =C2= =A0 0.430000 ( =C2=A00.426560)