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Feature #2172

Enumerable#chunk with no block

Added by Marc-Andre Lafortune almost 7 years ago. Updated 5 days ago.

Status:
Assigned
Priority:
Normal
[ruby-core:25912]

Description

=begin
What should "(1..3).chunk" (i.e. without a block) do?

It issued an
ArgumentError: tried to create Proc object without a block

I changed the error message to "no block given" which I hope to be more informative, but maybe there is something more useful to do here?

A default block of {|x| x} doesn't seem all that useful.

Returning an enumerator that, upon completion, will return an enumerator would probably be better, but could also be a bit confusing if someone doesn't realize he forgot to specify the block?

Thanks to Run Paint for raising the question when writing the rubyspec for #chunk.
=end

History

#1 Updated by Yui NARUSE almost 7 years ago

  • Status changed from Open to Assigned
  • Assignee changed from Yukihiro Matsumoto to Akira Tanaka

=begin

=end

#2 Updated by Marc-Andre Lafortune almost 7 years ago

  • Target version set to 1.9.2
  • Category set to core
  • Assignee changed from Akira Tanaka to Yukihiro Matsumoto

=begin

=end

#3 Updated by Marc-Andre Lafortune almost 7 years ago

  • Assignee changed from Yukihiro Matsumoto to Akira Tanaka

=begin

=end

#4 Updated by Marc-Andre Lafortune over 6 years ago

=begin
Maybe a default block of {|x| x} can be useful for some people...

http://stackoverflow.com/questions/2516312/remove-adjacent-identical-elements-in-a-ruby-array
=end

#5 Updated by Kazuhiro NISHIYAMA over 6 years ago

  • Target version changed from 1.9.2 to 2.0.0

=begin

=end

#6 [ruby-core:47020] Updated by Arnau Sanchez about 4 years ago

Any decision about this? For me it's a clear +1, chunking by the values unchanged is very common (not that it's representative, but I checked my code: 4 ocurrences of chunk, all with the identity block)

#7 [ruby-core:48520] Updated by Akira Tanaka almost 4 years ago

  • Target version changed from 2.0.0 to next minor
  • Description updated (diff)

#8 [ruby-core:77336] Updated by Marc-Andre Lafortune 5 days ago

  • Assignee changed from Akira Tanaka to Yukihiro Matsumoto

Matz, would you agree to return enumerator for chunk without a block?
This is useful in particular to chain it with with_index

A real case example is to summarize a list of integers into ranges. Currently, we need:

integers.enum_for(:chunk).with_index { |x, idx| x - idx }.map do |diff, group|
  [group.first, group.last]
end

Ref: http://stackoverflow.com/questions/8621733/how-do-i-summarize-array-of-integers-as-an-array-of-ranges

#9 [ruby-core:77337] Updated by Marc-Andre Lafortune 5 days ago

Forgot to note that the other possiblity suggested for chunk with no block can now be done clearly and succintly with chunk(&:itself), so there's no longer any doubt that the block without block should return an Enumerator

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