From: Fuad Saud Date: 2013-08-17T17:55:17-03:00 Subject: [ruby-core:56702] Re: [ruby-trunk - Feature #8772] Hash alias #| merge, and the case for Hash and Array polymorphism --001a11c39198aef06804e42aecaa Content-Type: text/plain; charset=ISO-8859-1 I don't think merge shoud be responsible for handling special cases like the array. You really should convert the array to a hash before. If you need to use such thing as reverse_merge!, why not use it like this: user_opts |= defaults being "|" an alias for anon destructive reverse_merge? I don't like havin "|" as a destructive operator. As for new operators, reverse_merge would be better represented as >>, but I don't think that's going to be approved. I'd still stick with << aliased to merge!, but | to reverse_merge is interesting as well. On Aug 17, 2013 4:32 PM, "alexeymuranov (Alexey Muranov)" < redmine@ruby-lang.org> wrote: > > Issue #8772 has been updated by alexeymuranov (Alexey Muranov). > > > trans (Thomas Sawyer) wrote: > > Actually I think #<< is good too. But it's definition needs to be a bit > more flexible than just merge. That's because it needs to do this: > > > > h = {} > > h << [:a,1] > > h << [:b,2] > > h #=> {:a=>1, :b=>2} > > Thomas, why h[:a] = 1, h[:b] = 2 wouldn't work for you? Or h << [[:a, 1], > [:b, 2]].to_h (#7292) ? > ---------------------------------------- > Feature #8772: Hash alias #| merge, and the case for Hash and Array > polymorphism > https://bugs.ruby-lang.org/issues/8772#change-41231 > > Author: trans (Thomas Sawyer) > Status: Open > Priority: Normal > Assignee: > Category: core > Target version: current: 2.1.0 > > > Ideally Hash and Array would be completely polymorphic in every manner in > which it is possible for them to be so. The reason for this is very simple. > It makes a programmer's life easier. For example, in a recent program I was > working on, I had a list of keyboard layouts. > > layouts = [layout1, layout2, layout3] > > Later I realized I wanted to identify them by a label not an index. So... > > layouts = {:foo => layout1, :bar => layout2, :baz => layout3} > > Unfortunately this broke my program in a number of places, and I had to go > through every use of `layouts` to translate what was an Array call into a > Hash call. If Array and and Hash were more polymorphic I would have only > had to adjust the places were I wanted to take advantage of the Hash. > Ideally almost nothing should have actually broken. > > The achieve optimal polymorphism between Hash and Array is to treat a > Hash's keys as indexes and its values as as the values of an array. e.g. > > a = [:a,:b,:c] > h = {0=>:a,1=>:b,2=>:c} > a.to_a #=> [:a,:b,:c] > h.to_a #=> [:a,:b,:c] > > Of course the ship has already sailed for some methods that are not > polymorphic, in particular #each. Nonetheless it would still be wise to try > to maximize the polymorphism going forward. (Perhaps even to be willing to > take a bold leap in Ruby 3.0 to break some backward compatibility to > improve upon this.) > > In the mean time, let us consider what it might mean for Hash#+ as an > alias for #merge, *if the above were so*: > > ([:a,:b] + [:c,:d]).to_a => [:a,:b,:c,:d] > ({0=>:a,1=>:b} + {2=>:c,3=>:d}).to_a => [:a,:b,:c,:d] > > ([:a,:b] + [:a,:b]).to_a => [:a,:b,:a,:b] > ({0=>:a,1=>:b} + {0=>:a,1=>:b}).to_a => [:a,:b] > > Damn! So it appears that #+ isn't the right operator. Let's try #| instead. > > ([:a,:b] | [:c,:d]).to_a => [:a,:b,:c,:d] > ({0=>:a,1=>:b} | {2=>:c,3=>:d}).to_a => [:a,:b,:c,:d] > > ([:a,:b] | [:a,:b]).to_a => [:a,:b] > ({0=>:a,1=>:b} | {0=>:a,1=>:b}).to_a => [:a,:b] > > Bingo. So I formally stand corrected. The best alias for merge is #| not > #+. > > Based on this line of reasoning I formally request the Hash#| be an alias > of Hash#merge. > > P.S. Albeit, given the current state of polymorphism between Ruby's Array > and Hash, and the fact that it will probably never be improved upon, I > doubt it really matters which operator is actually used. > > > > -- > http://bugs.ruby-lang.org/ > --001a11c39198aef06804e42aecaa Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable

I don't think merge shoud be responsible for handling special cases = like the array. You really should convert the array to a hash before.

If you need to use such thing as reverse_merge!, why not use it like thi= s:

user_opts |=3D defaults

being "|" an alias for anon destructive reverse_merge? I don&#= 39;t like havin "|" as a destructive operator.

As for new operators, reverse_merge would be better represented as >&= gt;, but I don't think that's going to be approved.

I'd still stick with << aliased to merge!, but | to reverse_me= rge is interesting as well.

On Aug 17, 2013 4:32 PM, "alexeymuranov (Al= exey Muranov)" <redmine@ru= by-lang.org> wrote:

Issue #8772 has been updated by alexeymuranov (Alexey Muranov).


trans (Thomas Sawyer) wrote:
> Actually I think #<< is good too. But it's definition needs = to be a bit more flexible than just merge. That's because it needs to d= o this:
>
> =A0 h =3D {}
> =A0 h << [:a,1]
> =A0 h << [:b,2]
> =A0 h =A0#=3D> {:a=3D>1, :b=3D>2}

Thomas, why h[:a] =3D 1, h[:b] =3D 2 wouldn't work for you? Or h <&l= t; [[:a, 1], [:b, 2]].to_h (#7292) ?
----------------------------------------
Feature #8772: Hash alias #| merge, and the case for Hash and Array polymor= phism
https://bugs.ruby-lang.org/issues/8772#change-41231

Author: trans (Thomas Sawyer)
Status: Open
Priority: Normal
Assignee:
Category: core
Target version: current: 2.1.0


Ideally Hash and Array would be completely polymorphic in every manner in w= hich it is possible for them to be so. The reason for this is very simple. = It makes a programmer's life easier. For example, in a recent program I= was working on, I had a list of keyboard layouts.

=A0 layouts =3D [layout1, layout2, layout3]

Later I realized I wanted to identify them by a label not an index. So...
=A0 layouts =3D {:foo =3D> layout1, :bar =3D> layout2, :baz =3D> l= ayout3}

Unfortunately this broke my program in a number of places, and I had to go = through every use of `layouts` to translate what was an Array call into a H= ash call. If Array and and Hash were more polymorphic I would have only had= to adjust the places were I wanted to take advantage of the Hash. Ideally = almost nothing should have actually broken.

The achieve optimal polymorphism between Hash and Array is to treat a Hash&= #39;s keys as indexes and its values as as the values of an array. e.g.

=A0 a =3D [:a,:b,:c]
=A0 h =3D {0=3D>:a,1=3D>:b,2=3D>:c}
=A0 a.to_a =A0#=3D> [:a,:b,:c]
=A0 h.to_a =A0#=3D> [:a,:b,:c]

Of course the ship has already sailed for some methods that are not polymor= phic, in particular #each. Nonetheless it would still be wise to try to max= imize the polymorphism going forward. (Perhaps even to be willing to take a= bold leap in Ruby 3.0 to break some backward compatibility to improve upon= this.)

In the mean time, let us consider what it might mean for Hash#+ as an alias= for #merge, *if the above were so*:

=A0 ([:a,:b] + [:c,:d]).to_a =A0 =A0 =A0 =A0 =A0 =A0 =3D> [:a,:b,:c,:d]<= br> =A0 ({0=3D>:a,1=3D>:b} + {2=3D>:c,3=3D>:d}).to_a =3D> [:a,:b= ,:c,:d]

=A0 ([:a,:b] + [:a,:b]).to_a =A0 =A0 =A0 =A0 =A0 =A0 =3D> [:a,:b,:a,:b]<= br> =A0 ({0=3D>:a,1=3D>:b} + {0=3D>:a,1=3D>:b}).to_a =3D> [:a,:b= ]

Damn! So it appears that #+ isn't the right operator. Let's try #| = instead.

=A0 ([:a,:b] | [:c,:d]).to_a =A0 =A0 =A0 =A0 =A0 =A0 =3D> [:a,:b,:c,:d]<= br> =A0 ({0=3D>:a,1=3D>:b} | {2=3D>:c,3=3D>:d}).to_a =3D> [:a,:b= ,:c,:d]

=A0 ([:a,:b] | [:a,:b]).to_a =A0 =A0 =A0 =A0 =A0 =A0 =3D> [:a,:b]
=A0 ({0=3D>:a,1=3D>:b} | {0=3D>:a,1=3D>:b}).to_a =3D> [:a,:b= ]

Bingo. So I formally stand corrected. The best alias for merge is #| not #+= .

Based on this line of reasoning I formally request the Hash#| be an alias o= f Hash#merge.

P.S. Albeit, given the current state of polymorphism between Ruby's Arr= ay and Hash, and the fact that it will probably never be improved upon, I d= oubt it really matters which operator is actually used.



--
http://bugs.ruby-l= ang.org/
--001a11c39198aef06804e42aecaa--