From: Brandon Weaver <keystonelemur@...>
Date: 2016-04-08T00:26:07-07:00
Subject: [ruby-core:74850] Re: [Ruby trunk Feature#12262] Anti-loop

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[1].each { puts 'looping'; sleep 1; redo }

On Fri, Apr 8, 2016 at 12:21 AM, <sawadatsuyoshi@gmail.com> wrote:

> Issue #12262 has been reported by Tsuyoshi Sawada.
>
> ----------------------------------------
> Feature #12262: Anti-loop
> https://bugs.ruby-lang.org/issues/12262
>
> * Author: Tsuyoshi Sawada
> * Status: Open
> * Priority: Normal
> * Assignee:
> ----------------------------------------
> The `loop` method continues by default, and requires the keyword `break`
> to escape. This is good when the continuing cases are the norm and the
> escaping cases are exceptional:
>
> ~~~RUBY
> loop do
>   ...
>   if ...
>     ...
>   elsif ...
>     ...
>   elsif ...
>     ...
>     break # breaks on exceptional cases
>   elsif ...
>     ...
>   else
>     ...
>   end
> end
> ~~~
>
> But when the continuing cases are exceptional and the escaping cases are
> the norm, the construction requires a lot of `break`, and it becomes
> cumbersome:
>
> ~~~RUBY
> loop do
>   ...
>   if ...
>     ...
>     break # lot of breaks
>   elsif ...
>     ...
>     break # lot of breaks
>   elsif ...
>     ...
>     break # lot of breaks
>   elsif ...
>     ...
>   else
>     ...
>     break # lot of breaks
>   end
> end
> ~~~
>
> I actually see this use case a lot when user input is asked with
> validation on a command line script.
>
> I request a `loop`-like method that works in the opposite way to `loop`,
> that is, it escapes (i.e., runs only once) by default, and requires a
> keyword to continue (perhaps `next`). The second code above would then be
> written like:
>
> ~~~RUBY
> some_loop_like_method do
>   ...
>   if ...
>     ...
>   elsif ...
>     ...
>   elsif ...
>     ...
>   elsif ...
>     ...
>     next # continues on exceptional cases
>   else
>     ...
>   end
> end
> ~~~
>
>
>
>
> --
> https://bugs.ruby-lang.org/
>
> Unsubscribe: <mailto:ruby-core-request@ruby-lang.org?subject=unsubscribe>
> <http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>
>

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<div dir=3D"ltr">







<p class=3D""><span class=3D"">[</span><span class=3D"">1</span><span class=
=3D"">].each { puts </span><span class=3D"">&#39;</span><span class=3D"">lo=
oping</span><span class=3D"">&#39;</span><span class=3D"">; sleep </span><s=
pan class=3D"">1</span><span class=3D"">; </span><span class=3D"">redo</spa=
n><span class=3D""> }</span></p></div><div class=3D"gmail_extra"><br><div c=
lass=3D"gmail_quote">On Fri, Apr 8, 2016 at 12:21 AM,  <span dir=3D"ltr">&l=
t;<a href=3D"mailto:sawadatsuyoshi@gmail.com" target=3D"_blank">sawadatsuyo=
shi@gmail.com</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" st=
yle=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Issue=
 #12262 has been reported by Tsuyoshi Sawada.<br>
<br>
----------------------------------------<br>
Feature #12262: Anti-loop<br>
<a href=3D"https://bugs.ruby-lang.org/issues/12262" rel=3D"noreferrer" targ=
et=3D"_blank">https://bugs.ruby-lang.org/issues/12262</a><br>
<br>
* Author: Tsuyoshi Sawada<br>
* Status: Open<br>
* Priority: Normal<br>
* Assignee:<br>
----------------------------------------<br>
The `loop` method continues by default, and requires the keyword `break` to=
 escape. This is good when the continuing cases are the norm and the escapi=
ng cases are exceptional:<br>
<br>
~~~RUBY<br>
loop do<br>
=C2=A0 ...<br>
=C2=A0 if ...<br>
=C2=A0 =C2=A0 ...<br>
=C2=A0 elsif ...<br>
=C2=A0 =C2=A0 ...<br>
=C2=A0 elsif ...<br>
=C2=A0 =C2=A0 ...<br>
=C2=A0 =C2=A0 break # breaks on exceptional cases<br>
=C2=A0 elsif ...<br>
=C2=A0 =C2=A0 ...<br>
=C2=A0 else<br>
=C2=A0 =C2=A0 ...<br>
=C2=A0 end<br>
end<br>
~~~<br>
<br>
But when the continuing cases are exceptional and the escaping cases are th=
e norm, the construction requires a lot of `break`, and it becomes cumberso=
me:<br>
<br>
~~~RUBY<br>
loop do<br>
=C2=A0 ...<br>
=C2=A0 if ...<br>
=C2=A0 =C2=A0 ...<br>
=C2=A0 =C2=A0 break # lot of breaks<br>
=C2=A0 elsif ...<br>
=C2=A0 =C2=A0 ...<br>
=C2=A0 =C2=A0 break # lot of breaks<br>
=C2=A0 elsif ...<br>
=C2=A0 =C2=A0 ...<br>
=C2=A0 =C2=A0 break # lot of breaks<br>
=C2=A0 elsif ...<br>
=C2=A0 =C2=A0 ...<br>
=C2=A0 else<br>
=C2=A0 =C2=A0 ...<br>
=C2=A0 =C2=A0 break # lot of breaks<br>
=C2=A0 end<br>
end<br>
~~~<br>
<br>
I actually see this use case a lot when user input is asked with validation=
 on a command line script.<br>
<br>
I request a `loop`-like method that works in the opposite way to `loop`, th=
at is, it escapes (i.e., runs only once) by default, and requires a keyword=
 to continue (perhaps `next`). The second code above would then be written =
like:<br>
<br>
~~~RUBY<br>
some_loop_like_method do<br>
=C2=A0 ...<br>
=C2=A0 if ...<br>
=C2=A0 =C2=A0 ...<br>
=C2=A0 elsif ...<br>
=C2=A0 =C2=A0 ...<br>
=C2=A0 elsif ...<br>
=C2=A0 =C2=A0 ...<br>
=C2=A0 elsif ...<br>
=C2=A0 =C2=A0 ...<br>
=C2=A0 =C2=A0 next # continues on exceptional cases<br>
=C2=A0 else<br>
=C2=A0 =C2=A0 ...<br>
=C2=A0 end<br>
end<br>
~~~<br>
<span class=3D"HOEnZb"><font color=3D"#888888"><br>
<br>
<br>
<br>
--<br>
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</font></span></blockquote></div><br></div>

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