From: Nathan Broadbent <nathan.f77@...>
Date: 2012-10-31T04:23:07+09:00
Subject: [ruby-core:48626] Re: [ruby-trunk - Feature #7241][Open] Enumerable#to_h proposal

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> `each_with_object` isn't specific to hashes, and isn't doing list
translation like `map` does.

I think `each_with_hash` would be really useful. Not only for cases where
you would normally use `each_with_object({})`, but it would also be much
nicer to write `each_with_hash([])` instead of
`each_with_object(Hash.new([]))`.

I had another idea that I'd like to mention: Since you'd often be using
default hash values with `each_with_hash`, I would find it useful if there
was an easy way to convert the default value into a proc that sets the hash
value when a key is looked up, instead of writing  `-> hash, key {
hash[key] = <default> }`.
My intention is to be able to write code like: `[1, 2,
1].each_with_hash([], true) {|h, v| h[v] << v ** 2 }`, where the `true` arg
would convert the default value into the proc above. (Personal preference,
but I don't really like `+= []`). Does anyone else think that could be
useful?


> IOW, it sounds perfect for ActiveSupport. ;-)

Let me know if you think `each_with_hash` is a good idea, and if it should
be added to ActiveSupport. I could open a pull request on Rails or start a
new Issue for Ruby :)


Best,
Nathan

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<span class=3D"Apple-style-span" style>&gt; `each_with_object` isn&#39;t sp=
ecific to hashes, and isn&#39;t doing list<br>translation like `map` does.<=
/span><div>=A0</div><div>I think `each_with_hash` would be really useful. N=
ot only for cases where you would normally use `each_with_object({})`, but =
it would also be much nicer to write `each_with_hash([])` instead of `each_=
with_object(Hash.new([]))`.</div>
<div><br></div><div>I had another idea that I&#39;d like to mention: Since =
you&#39;d often be using default hash values with `each_with_hash`, I would=
 find it useful if there was an easy way to convert the default value into =
a proc that sets the hash value when a key is looked up, instead of writing=
 =A0`-&gt; hash, key { hash[key] =3D &lt;default&gt; }`.</div>
My intention is to be able to write code like: `[1, 2, 1].each_with_hash([]=
, true) {|h, v| h[v] &lt;&lt; v ** 2 }`, where the `true` arg would convert=
 the default value into the proc above. (Personal preference, but I don&#39=
;t really like `+=3D []`).=A0<span class=3D"Apple-style-span" style>Does an=
yone else think that could be useful?</span><div>
<br></div><div><br></div><div><span class=3D"Apple-style-span" style>&gt; I=
OW, it sounds perfect for ActiveSupport. ;-)</span></div><div><span class=
=3D"Apple-style-span" style><br></span></div><div><span class=3D"Apple-styl=
e-span" style>Let me know if you think `each_with_hash` is a good idea, and=
 if it should be added to ActiveSupport. I could open a pull request on Rai=
ls or start a new Issue for Ruby :)<span></span></span></div>
<div><span class=3D"Apple-style-span" style><br></span></div><div><span cla=
ss=3D"Apple-style-span" style><br></span></div><div><span class=3D"Apple-st=
yle-span" style>Best,</span></div><div><span class=3D"Apple-style-span" sty=
le>Nathan</span></div>
<div><div><div><div></div></div></div></div>

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