From: Robert Klemme <shortcutter@...>
Date: 2013-07-09T06:37:23+09:00
Subject: Re: A very half-baked idea: setting local variables

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On Mon, Jul 8, 2013 at 11:06 PM, Hal Fulton <rubyhacker@gmail.com> wrote:

> I'm sure this nonexistent feature is not in great demand, but there have
> been different times that I (and other people) have wanted it.
>
> This is not a "really serious" proposal, but I wanted to see what other
> people's comments were about lengthy multiple assignments and
> how to deal with them.
>
> Sometimes I wish I had an alternative way to do assignment.
>
> Example:
>
>   foo, bar, baz, alpha, beta, gamma, fred, bill, joey = *values
>
> In a case like that, my eye has to scan a long way to the right
> before finding the equal sign and grasping that this is a multiple
> assignment.
>
> I like this better:
>
>   vars = [:foo, :bar, :baz, :alpha, :beta, :gamma, :fred, :bill, :joey]
>   assign values, vars
>
> Note that this wouldn't be a method call (like alias_method) but
> a keyword (like alias) unless "binding of caller" was permitted...
> which is another thing I've wanted but I suppose will never
> happen.
>
> Comments, questions, projectiles?
>

At the moment there is no other way I am aware of to introduce local
variables _at runtime_.  While you can do things like eval("foo = 123") the
remaining code won't be using the local variable.

$ ruby -e 'b=binding;eval("x=10", b);puts x'
-e:1:in `<main>': undefined local variable or method `x' for main:Object
(NameError)
$ ruby -e 'b=binding;eval("x=10", b);eval("puts x", b)'
10


How about

data = {}
[:foo, :bar, :baz, :alpha, :beta, :gamma, :fred, :bill,
:joey].each_with_index do |s,i|
  data[s] = values[i]
end

puts data[:baz]

or even

data = [:foo, :bar, :baz, :alpha, :beta, :gamma, :fred, :bill,
:joey].each_with_index.each_with_object {} do |(s,i), d|
  d[s] = values[i]
end

?

Cheers

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/

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<div dir=3D"ltr"><br><div class=3D"gmail_extra"><br><br><div class=3D"gmail=
_quote">On Mon, Jul 8, 2013 at 11:06 PM, Hal Fulton <span dir=3D"ltr">&lt;<=
a href=3D"mailto:rubyhacker@gmail.com" target=3D"_blank">rubyhacker@gmail.c=
om</a>&gt;</span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-=
left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;p=
adding-left:1ex"><div dir=3D"ltr">I&#39;m sure this nonexistent feature is =
not in great demand, but there have<div>
been different times that I (and other people) have wanted it.</div><div><b=
r></div><div>This is not a &quot;really serious&quot; proposal, but I wante=
d to see what other</div>
<div>people&#39;s comments were about lengthy multiple assignments and</div=
><div>how to deal with them.</div><div><br></div><div>Sometimes I wish I ha=
d an alternative way to do assignment.</div><div>
<br></div><div>Example:</div><div><br></div><div>=A0 foo, bar, baz, alpha, =
beta, gamma, fred, bill, joey =3D *values</div><div><br></div><div>In a cas=
e like that, my eye has to scan a long way to the right</div>
<div>before finding the equal sign and grasping that this is a multiple</di=
v><div>assignment.</div><div><br></div><div>I like this better:</div><div><=
br></div><div>=A0 vars =3D [:foo, :bar, :baz, :alpha, :beta, :gamma, :fred,=
 :bill, :joey]</div>

<div>=A0 assign values, vars</div><div><br></div><div>Note that this wouldn=
&#39;t be a method call (like alias_method) but=A0</div><div>a keyword (lik=
e alias) unless &quot;binding of caller&quot; was permitted...</div>
<div>which is another thing I&#39;ve wanted but I suppose will never</div><=
div>happen.</div><div><br></div><div>Comments, questions, projectiles?</div=
><span class=3D""><font color=3D"#888888"><div></div></font></span></div></=
blockquote>
</div><div class=3D"gmail_extra"><br></div>At the moment there is no other =
way I am aware of to introduce local variables _at runtime_. =A0While you c=
an do things like eval(&quot;foo =3D 123&quot;) the remaining code won&#39;=
t be using the local variable.</div>
<div class=3D"gmail_extra"><br></div><div class=3D"gmail_extra"><div class=
=3D"gmail_extra">$ ruby -e &#39;b=3Dbinding;eval(&quot;x=3D10&quot;, b);put=
s x&#39;</div><div class=3D"gmail_extra">-e:1:in `&lt;main&gt;&#39;: undefi=
ned local variable or method `x&#39; for main:Object (NameError)</div>
<div><div>$ ruby -e &#39;b=3Dbinding;eval(&quot;x=3D10&quot;, b);eval(&quot=
;puts x&quot;, b)&#39;</div><div>10</div></div><div><br></div><div><br></di=
v><div>How about</div><div><br></div><div>data =3D {}</div><div>[:foo, :bar=
, :baz, :alpha, :beta, :gamma, :fred, :bill, :joey].each_with_index do |s,i=
|<br>
</div><div>=A0 data[s] =3D values[i]</div><div>end</div><div><br></div><div=
>puts data[:baz]<br></div><div><br></div><div>or even</div><div><br></div><=
div>data =3D [:foo, :bar, :baz, :alpha, :beta, :gamma, :fred, :bill, :joey]=
.each_with_index.each_with_object {} do |(s,i), d|</div>
<div>=A0 d[s] =3D values[i]</div><div>end</div><div><br></div><div>?</div><=
div><br></div></div><div class=3D"gmail_extra">Cheers</div><div class=3D"gm=
ail_extra"><br></div><div class=3D"gmail_extra">robert<br clear=3D"all"><di=
v><br></div>
-- <br>remember.guy do |as, often| as.you_can - without end<br><a href=3D"h=
ttp://blog.rubybestpractices.com/">http://blog.rubybestpractices.com/</a>
</div></div>

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