Feature #2172: Enumerable#chunk with no block

• Status: Closed
• Assignee: matz (Yukihiro Matsumoto)
• Target version: -

[marcandre (Marc-Andre Lafortune)]

=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

[naruse (Yui NARUSE)]

• Status changed from Open to Assigned
• Assignee changed from matz (Yukihiro Matsumoto) to akr (Akira Tanaka)

[marcandre (Marc-Andre Lafortune)]

• Category set to core
• Assignee changed from akr (Akira Tanaka) to matz (Yukihiro Matsumoto)
• Target version set to 1.9.2

[marcandre (Marc-Andre Lafortune)]

• Assignee changed from matz (Yukihiro Matsumoto) to akr (Akira Tanaka)

[marcandre (Marc-Andre Lafortune)]

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

[znz (Kazuhiro NISHIYAMA)]

• Target version changed from 1.9.2 to 2.0.0

[tokland (Arnau Sanchez)]

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)

[akr (Akira Tanaka)]

• Description updated (diff)
• Target version changed from 2.0.0 to 2.6

[marcandre (Marc-Andre Lafortune)]

• Assignee changed from akr (Akira Tanaka) to matz (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

[marcandre (Marc-Andre Lafortune)]

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

[matz (Yukihiro Matsumoto)]

Now it sounds reasonable. Marc-Andre, could you implement it?

Matz.

[marcandre (Marc-Andre Lafortune)]

Great, thanks!

Done for chunk.

Matz, I imagine I should do the same for chunk_while, slice_after, slice_before and slice_when, right?

[marcandre (Marc-Andre Lafortune)]

• Status changed from Assigned to Closed

Closing, created #12813 instead.