From: merch-redmine@jeremyevans.net
To: ruby-core@ruby-lang.org
Subject: [ruby-core:91594] [Ruby trunk Feature#15612] A construct to restrict the scope of local variables
Date: Tue, 19 Feb 2019 15:15:48 +0000 (UTC) [thread overview]
Message-ID: <redmine.journal-76856.20190219151546.7fe3467b7f2dd006@ruby-lang.org> (raw)
In-Reply-To: redmine.issue-15612.20190219124221@ruby-lang.org
Issue #15612 has been updated by jeremyevans0 (Jeremy Evans).
sawa (Tsuyoshi Sawada) wrote:
> In order to improve readability of the code by explicitly indicating the scope of such local variables, and to avoid pollution by the variable, I propose to have some construct to restrict the scope of local variables.
>
> One possibility, without adding a new keyword to the current syntax, is to use the `begin`...`end` construct. The expected behavior would be:
>
> ```ruby
> begin
> foo = "foo"
> foo # => "foo"
> end
> foo # => `nil`, or "Undefined local variable or method error"
> ```
This would definitely break existing code. There is a lot of code that expects to be able to access local variables first assigned inside a begin/end block after the begin/end block.
As blocks already do what you want, why not just:
```ruby
tap do
foo = "foo"
foo # => "foo"
end
foo # => NameError
```
```ruby
foo = "bar"
tap do
foo = "foo"
foo # => "foo"
end
foo # => "foo"
```
You can substitute another method that yields once for `tap` if you want.
----------------------------------------
Feature #15612: A construct to restrict the scope of local variables
https://bugs.ruby-lang.org/issues/15612#change-76856
* Author: sawa (Tsuyoshi Sawada)
* Status: Feedback
* Priority: Normal
* Assignee:
* Target version:
----------------------------------------
We sometimes have local variables that are to be used only to keep track of some temporal states/values during a short routine:
```ruby
...
foo = some_initial_value
some_routine_that_uses_foo
...
```
Currently, the scope of local variables are either a proc, a block, `loop` body, a method definition, or a class/module definition, but such routines are sometimes just only a part of them.
In order to improve readability of the code by explicitly indicating the scope of such local variables, and to avoid pollution by the variable, I propose to have some construct to restrict the scope of local variables.
One possibility, without adding a new keyword to the current syntax, is to use the `begin`...`end` construct. The expected behavior would be:
```ruby
begin
foo = "foo"
foo # => "foo"
end
foo # => `nil`, or "Undefined local variable or method error"
```
```ruby
foo = "bar"
begin
foo = "foo"
foo # => "foo"
end
foo # => "bar"
```
Or, does this break the existing code too much? If so, can a new construct be added to the current syntax?
--
https://bugs.ruby-lang.org/
next prev parent reply other threads:[~2019-02-19 15:15 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <redmine.issue-15612.20190219124221@ruby-lang.org>
2019-02-19 12:42 ` [ruby-core:91591] [Ruby trunk Feature#15612] A construct to restrict the scope of local variables sawadatsuyoshi
2019-02-19 13:28 ` [ruby-core:91592] " matz
2019-02-19 14:38 ` [ruby-core:91593] " shevegen
2019-02-19 15:15 ` merch-redmine [this message]
2019-02-19 22:39 ` [ruby-core:91596] " duerst
2019-02-20 1:55 ` [ruby-core:91598] " nobu
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