I think Hash#<< would be a good alias for Hash#merge! (the in place =
form, since Array#<< and String#<< both modify the receiver in place).

That does not preclude Hash#| being used for reverse_merge =
functionality.

Dave

On Aug 13, 2013, at 12:21 PM, fuadksd (Fuad Saud) wrote:

>=20
> Issue #8772 has been updated by fuadksd (Fuad Saud).
>=20
>=20
> This wouldn't head towards any polymorphic approach, but isn't << a =
better operator for merging? It fells like you're shoving all the =
contents of the argument to the receiver hash. I think it represents =
better the functionality of the method.
> ----------------------------------------
> Feature #8772: Hash alias #| merge, and the case for Hash and Array =
polymorphism
> https://bugs.ruby-lang.org/issues/8772#change-41142
>=20
> Author: trans (Thomas Sawyer)
> Status: Open
> Priority: Normal
> Assignee:=20
> Category: core
> Target version: current: 2.1.0
>=20
>=20
> 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.
>=20
>  layouts =3D [layout1, layout2, layout3]
>=20
> Later I realized I wanted to identify them by a label not an index. =
So...
>=20
>  layouts =3D {:foo =3D> layout1, :bar =3D> layout2, :baz =3D> layout3}
>=20
> 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.=20
>=20
> 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.
>=20
>  a =3D [:a,:b,:c]
>  h =3D {0=3D>:a,1=3D>:b,2=3D>:c}
>  a.to_a  #=3D> [:a,:b,:c]
>  h.to_a  #=3D> [:a,:b,:c]
>=20
> 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.)
>=20
> In the mean time, let us consider what it might mean for Hash#+ as an =
alias for #merge, *if the above were so*:
>=20
>  ([:a,:b] + [:c,:d]).to_a             =3D> [:a,:b,:c,:d]
>  ({0=3D>:a,1=3D>:b} + {2=3D>:c,3=3D>:d}).to_a =3D> [:a,:b,:c,:d]
>=20
>  ([:a,:b] + [:a,:b]).to_a             =3D> [:a,:b,:a,:b]
>  ({0=3D>:a,1=3D>:b} + {0=3D>:a,1=3D>:b}).to_a =3D> [:a,:b]
>=20
> Damn! So it appears that #+ isn't the right operator. Let's try #| =
instead.
>=20
>  ([:a,:b] | [:c,:d]).to_a             =3D> [:a,:b,:c,:d]
>  ({0=3D>:a,1=3D>:b} | {2=3D>:c,3=3D>:d}).to_a =3D> [:a,:b,:c,:d]
>=20
>  ([:a,:b] | [:a,:b]).to_a             =3D> [:a,:b]
>  ({0=3D>:a,1=3D>:b} | {0=3D>:a,1=3D>:b}).to_a =3D> [:a,:b]
>=20
> Bingo. So I formally stand corrected. The best alias for merge is #| =
not #+.=20
>=20
> Based on this line of reasoning I formally request the Hash#| be an =
alias of Hash#merge.
>=20
> 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.
>=20
>=20
>=20
> --=20
> http://bugs.ruby-lang.org/