Forum: Ruby-core [ruby-trunk - Feature #7654][Open] Add optional code block to IO::readlines

Issue #7654 has been reported by shock_one (Володимир Шацький).

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Feature #7654: Add optional code block to IO::readlines
https://bugs.ruby-lang.org/issues/7654

Author: shock_one (Володимир Шацький)
Status: Open
Priority: Normal
Assignee:
Category: core
Target version:


Of course, we always can write something like
File.readlines('/home/shock_one/test.rb').map{ |line| line.upcase }
but this way we create unneeded intermediate array which can be pretty 
big.
There is also a method IO::foreach, but it doesn't collect return 
values.
Besides it seems pretty logical and natural to have a block in this 
method.

Issue #7654 has been updated by shock_one (Володимир Шацький).


Just to be clear: code block will allow to write the first code snippet 
as follows:
data = File.readlines('/home/shock_one/test.rb'){ |line| line.upcase }
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Feature #7654: Add optional code block to IO::readlines
https://bugs.ruby-lang.org/issues/7654#change-35207

Author: shock_one (Володимир Шацький)
Status: Open
Priority: Normal
Assignee:
Category: core
Target version:


Of course, we always can write something like
File.readlines('/home/shock_one/test.rb').map{ |line| line.upcase }
but this way we create unneeded intermediate array which can be pretty 
big.
There is also a method IO::foreach, but it doesn't collect return 
values.
Besides it seems pretty logical and natural to have a block in this 
method.

Issue #7654 has been updated by Eregon (Benoit Daloze).


Why not

    File.foreach('test.rb').map { |line| line.upcase }

?
It does not create an intermediary Array.
If you need to do other operations lazily (without an intermediate 
result), you could use #lazy:

    File.foreach('test.rb').lazy.select { |line| line.start_with? '/' 
}.map { |line| line.upcase }.to_a
----------------------------------------
Feature #7654: Add optional code block to IO::readlines
https://bugs.ruby-lang.org/issues/7654#change-35210

Author: shock_one (Володимир Шацький)
Status: Open
Priority: Normal
Assignee:
Category: core
Target version:


Of course, we always can write something like
File.readlines('/home/shock_one/test.rb').map{ |line| line.upcase }
but this way we create unneeded intermediate array which can be pretty 
big.
There is also a method IO::foreach, but it doesn't collect return 
values.
Besides it seems pretty logical and natural to have a block in this 
method.

Issue #7654 has been updated by Eregon (Benoit Daloze).


But of course the main memory usage here are likely String instances, so 
you should update them in place if possible:

    File.foreach('test.rb').map { |line| line.upcase!; line }
    # or
    lines = File.readlines('file.c')
    lines.each(&:upcase!)
----------------------------------------
Feature #7654: Add optional code block to IO::readlines
https://bugs.ruby-lang.org/issues/7654#change-35211

Author: shock_one (Володимир Шацький)
Status: Open
Priority: Normal
Assignee:
Category: core
Target version:


Of course, we always can write something like
File.readlines('/home/shock_one/test.rb').map{ |line| line.upcase }
but this way we create unneeded intermediate array which can be pretty 
big.
There is also a method IO::foreach, but it doesn't collect return 
values.
Besides it seems pretty logical and natural to have a block in this 
method.

Issue #7654 has been updated by Eregon (Benoit Daloze).


(There is also Array#map!)
----------------------------------------
Feature #7654: Add optional code block to IO::readlines
https://bugs.ruby-lang.org/issues/7654#change-35212

Author: shock_one (Володимир Шацький)
Status: Open
Priority: Normal
Assignee:
Category: core
Target version:


Of course, we always can write something like
File.readlines('/home/shock_one/test.rb').map{ |line| line.upcase }
but this way we create unneeded intermediate array which can be pretty 
big.
There is also a method IO::foreach, but it doesn't collect return 
values.
Besides it seems pretty logical and natural to have a block in this 
method.

Issue #7654 has been updated by shock_one (Володимир Шацький).


Thank you, Eregon, especially for in place methods. I should definitely 
pay more attention to them - functional languages made me a little 
suspicious of this sort of things.
But I still think it would be nice to have an optional block in 
IO::readlines, at least for convenience. Enumerable#grep has similar 
behavior and I find it really cool and useful. Also this change doesn't 
break anything, is easy to implement and makes the code more concise.
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Feature #7654: Add optional code block to IO::readlines
https://bugs.ruby-lang.org/issues/7654#change-35213

Author: shock_one (Володимир Шацький)
Status: Open
Priority: Normal
Assignee:
Category: core
Target version:


Of course, we always can write something like
File.readlines('/home/shock_one/test.rb').map{ |line| line.upcase }
but this way we create unneeded intermediate array which can be pretty 
big.
There is also a method IO::foreach, but it doesn't collect return 
values.
Besides it seems pretty logical and natural to have a block in this 
method.

Issue #7654 has been updated by ko1 (Koichi Sasada).


next minor issue or 2.0.0 issue?

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Feature #7654: Add optional code block to IO::readlines
https://bugs.ruby-lang.org/issues/7654#change-35604

Author: shock_one (Володимир Шацький)
Status: Open
Priority: Normal
Assignee:
Category: core
Target version:


Of course, we always can write something like
File.readlines('/home/shock_one/test.rb').map{ |line| line.upcase }
but this way we create unneeded intermediate array which can be pretty 
big.
There is also a method IO::foreach, but it doesn't collect return 
values.
Besides it seems pretty logical and natural to have a block in this 
method.

Issue #7654 has been updated by drbrain (Eric Hodel).


I think next minor. It is a new feature but trunk is closed for new 
features.
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Feature #7654: Add optional code block to IO::readlines
https://bugs.ruby-lang.org/issues/7654#change-35638

Author: shock_one (Володимир Шацький)
Status: Open
Priority: Normal
Assignee:
Category: core
Target version:


Of course, we always can write something like
File.readlines('/home/shock_one/test.rb').map{ |line| line.upcase }
but this way we create unneeded intermediate array which can be pretty 
big.
There is also a method IO::foreach, but it doesn't collect return 
values.
Besides it seems pretty logical and natural to have a block in this 
method.

Issue #7654 has been updated by drbrain (Eric Hodel).

Target version set to next minor


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Feature #7654: Add optional code block to IO::readlines
https://bugs.ruby-lang.org/issues/7654#change-35643

Author: shock_one (Володимир Шацький)
Status: Open
Priority: Normal
Assignee:
Category: core
Target version: next minor


Of course, we always can write something like
File.readlines('/home/shock_one/test.rb').map{ |line| line.upcase }
but this way we create unneeded intermediate array which can be pretty 
big.
There is also a method IO::foreach, but it doesn't collect return 
values.
Besides it seems pretty logical and natural to have a block in this 
method.

Issue #7654 has been updated by ko1 (Koichi Sasada).

Assignee set to matz (Yukihiro Matsumoto)


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Feature #7654: Add optional code block to IO::readlines
https://bugs.ruby-lang.org/issues/7654#change-36742

Author: shock_one (Володимир Шацький)
Status: Open
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: core
Target version: next minor


Of course, we always can write something like
File.readlines('/home/shock_one/test.rb').map{ |line| line.upcase }
but this way we create unneeded intermediate array which can be pretty 
big.
There is also a method IO::foreach, but it doesn't collect return 
values.
Besides it seems pretty logical and natural to have a block in this 
method.