[ruby-core:62768] [ruby-trunk - Bug #1893] Recursive Enumerable#join is surprising

Issue #1893 has been updated by Yui NARUSE.

Related to Feature #7226: Added #join method as a shortcut for to_a.join added

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Bug #1893: Recursive Enumerable#join is surprising
https://bugs.ruby-lang.org/issues/1893#change-46886

* Author: Jeremy Kemper
* Status: Closed
* Priority: Normal
* Assignee: Yukihiro Matsumoto
* Category: core
* Target version: 
* ruby -v: ruby 1.9.2dev (2009-08-06) [i386-darwin9.7.0]
* Backport: 
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=begin
 >> Bar = Struct.new(:a, :b)
 => Bar
 >> bars = [Bar.new('1', '2'), Bar.new('3', '4')]
 => [#<struct Bar a="1", b="2">, #<struct Bar a="3", b="4">]
 >> bars * '--'
 => "1--2--3--4"
 
 Surprising? It looks like joining Arrays not Structs. Let's define to_s:
 
 >> class Bar; def to_s; 'foo' end end
 => nil
 >> bars * '--'
 => "1--2--3--4"
 
 Doesn't work! Strange. But remove to_a and it works!
 
 >> class Bar; undef_method :to_a end
 => Bar
 >> bars * '--'
 => "foo--foo"
 
 Also note that defining to_str works because ary_join_1 checks rb_check_string_type first, then rb_check_convert_type:
 
 >> class Bar; def to_str; 'baz' end end
 => nil
 >> bars * '--'
 => "baz--baz"
 
 See r23951 for the change:
 * array.c (ary_join_1): recursive join for Enumerators (and objects with #to_a).
 
 There are two solutions:
 * remove Struct#to_a, or
 * tighten the recursive join check for arrays
 
 I think we need a to_ary (like to_str) for the recursive array case instead of using to_a.
=end




-- 
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