[#92070] [Ruby trunk Feature#15667] Introduce malloc_trim(0) in full gc cycles — sam.saffron@...
Issue #15667 has been updated by sam.saffron (Sam Saffron).
3 messages
2019/04/01
[ruby-core:92492] [Ruby trunk Feature#10394] An instance method on Enumerator that evaluates the block under with self being the block variable.
From:
nobu@...
Date:
2019-04-30 11:58:12 UTC
List:
ruby-core #92492
Issue #10394 has been updated by nobu (Nobuyoshi Nakada).
Isn't it `instance_eval`?
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Feature #10394: An instance method on Enumerator that evaluates the block under with self being the block variable.
https://bugs.ruby-lang.org/issues/10394#change-77841
* Author: sawa (Tsuyoshi Sawada)
* Status: Feedback
* Priority: Normal
* Assignee:
* Target version:
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**Background**
There has been desire to omit the `| |` and the explicit receiver in a block used with an enumerator or an enumerable. Currently, when the content of the block is a single method that takes no argument, symbol-to-proc is used with the `&` syntax so that:
~~~ruby
["foo", "bar"].map{|s| s.upcase}
~~~
can be written as:
~~~ruby
["foo", "bar"].map(&:upcase)
~~~
There has repeated been proposals (#8987, #9076, #10318) that express this desire to do this even when the block involves a method chain or a method with arguments like the following:
~~~ruby
["foo", "bar"].map{|s| s.concat("ber")}
[" foo ", "\tbar\n"].map{|s| s.strip.upcase}
~~~
Focus has been on modifying how a block is passed to the enumerable/enumerator, and there has not been consensus on how the syntax should be.
**Proposal**
Unlike the earlier proposals, I suggest that there should be an instance method on `Enumerator`, let's say `Enumerator#as_self`, that evaluates the block each time with `self` being the block variable that would be passed otherwise. With such method, the cases above would be written like this:
~~~ruby
["foo", "bar"].map.as_self{concat("ber")}
[" foo ", "\tbar\n"].map.as_self{strip.upcase}
~~~
This adds no modification to the syntax, it just requires a new method `Enumerator#as_self` to be implemented. I consider this method being along the lines of `Enumerator#with_index`, `Enumerator#with_object`; it intervenes between an enumerator (related to a block-taking method) and a block, and let the block-taking method work in a modified way.
It resembles `instance_eval`, but is different in that it assigns to `self` what would be a block variable (which changes for each iteration), instead of assigning the receiver.
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