From: matz@ruby-lang.org
To: ruby-core@ruby-lang.org
Subject: [ruby-core:71888] [Ruby trunk - Feature #11737] [Rejected] Pass in expression to then block in `case expression`
Date: Mon, 07 Dec 2015 07:41:36 +0000 [thread overview]
Message-ID: <redmine.journal-55294.20151207074135.81865244c07bf5ff@ruby-lang.org> (raw)
In-Reply-To: redmine.issue-11737.20151124205922@ruby-lang.org
Issue #11737 has been updated by Yukihiro Matsumoto.
Status changed from Open to Rejected
It's not worth adding special expression or variable for retrieving the when value.
Just use assignment.
Matz.
----------------------------------------
Feature #11737: Pass in expression to then block in `case expression`
https://bugs.ruby-lang.org/issues/11737#change-55294
* Author: Daniel P. Clark
* Status: Rejected
* Priority: Normal
* Assignee:
----------------------------------------
Ruby's `case <expression>` scenario allows the expression to be tested in the `when` test with `:===`, but in the then block the expression is not accessible. Only if the expression has been assigned to a variable beforehand can it be checked.
~~~ruby
case 4
when ->i{ puts :when; true}
->i{ puts i}
else
:foo
end
# when
# => #<Proc:0x00000000d91e58@(irb):16 (lambda)>
case 4
when ->i{ puts :when; true}
puts _
else
:foo
end
# when
# #<Proc:0x00000000d91e58@(irb):16 (lambda)>
# => nil
case 4
when 4
then _
end
# => nil
case 4
when 4
then ->i{puts i}
end
# => #<Proc:0x000000015f9be0@(irb):36 (lambda)>
~~~
If some one wanted to give an expression after case that wasn't assigned to a variable then there is no access to it in the then block.
I suggest assigning the expression to the `_` variable during a case/when/then scenario. Here's a rather contrived example use case.
~~~ruby
case Enumerator.new do |y| y << 1; y << 2; y << 3; end
when ->e{ 2.times e.next; true}
then _.peek
end == 3
~~~
--
https://bugs.ruby-lang.org/
next prev parent reply other threads:[~2015-12-07 7:10 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <redmine.issue-11737.20151124205922@ruby-lang.org>
2015-11-24 20:59 ` [ruby-core:71664] [Ruby trunk - Feature #11737] [Open] Pass in expression to then block in `case expression` 6ftdan
2015-11-24 21:03 ` [ruby-core:71665] [Ruby trunk - Feature #11737] " 6ftdan
2015-11-25 18:56 ` [ruby-core:71686] " 6ftdan
2015-11-28 0:10 ` [ruby-core:71715] " nobu
2015-11-28 8:56 ` [ruby-core:71719] " 6ftdan
2015-12-03 4:07 ` [ruby-core:71810] " s.wanabe
2015-12-04 23:43 ` [ruby-core:71839] " 6ftdan
2015-12-07 7:41 ` matz [this message]
2015-12-07 11:22 ` [ruby-core:71902] " 6ftdan
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