[ruby-core:89210] [Ruby trunk Bug#15174] Sorting array of elements using "&:size" block, in which more than 1 element

Issue #15174 has been updated by jeremyevans0 (Jeremy Evans).


You want `sort_by`, not `sort`:

~~~ ruby
[1..2, 4..5].sort_by(&:size)
# => [1..2, 4..5]
~~~

The difference in behavior between `{ |x| x.size }` and `(&:size)` is due to how ruby handles `Symbol#to_proc` when multiple arguments are yielded.  If a block yields multiple arguments, `Symbol#to_proc` is the equivalent of `first_arg.send(symbol, *remaining_args)`, not `first_arg.send(symbol)` or `[first_arg, *remaining_args].send(symbol)`.  Example:

~~~ ruby
def b(*a)
  p [self, a]
  1
end

[1..2, 4..5].sort{|x| x.b}
# => [4..5, 1..2]
# output:
# [1..2, []]

[1..2, 4..5].sort(&:b)
# => [4..5, 1..2]
# output:
# [1..2, [4..5]]
~~~

`Range#size` does not take an argument, hence the ArgumentError when you are using `sort(&:size)` with an array of Range instances.

I believe this behavior is expected (see `vm_yield_with_symbol` in `vm_insnhelper.c`).  However, a more experienced rubyist should probably confirm that.

----------------------------------------
Bug #15174: Sorting array of elements using "&:size" block, in which more than 1 element
https://bugs.ruby-lang.org/issues/15174#change-74234

* Author: Mr_Cartoon (Sviat Safronov)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 2.5.1, 2.6.0-preview2
* Backport: 2.3: UNKNOWN, 2.4: UNKNOWN, 2.5: UNKNOWN
----------------------------------------
Example with ranges(first with what defined bug), but also tested on strings, symbols, integers
Good
~~~ ruby
[1..2].sort { |x| x.size }
[1..2, 4..5].sort { |x| x.size }
[1..2].sort(&:size)
~~~


Bad
~~~ ruby
[1..2, 4..5].sort(&:size)
~~~

Traceback (most recent call last):
        4: from /home/sviat/.rvm/rubies/ruby-2.6.0-preview2/bin/irb:11:in `<main>'
        3: from (irb):3
        2: from (irb):3:in `sort'
        1: from (irb):3:in `size'
ArgumentError (wrong number of arguments (given 1, expected 0))


Tested ruby versions: 2.5.1, 2.6.0-preview2



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