Issue #7803 has been reported by sawa (Tsuyoshi Sawada).

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RubySpec #7803: RDoc documentation: `Array#&` clarification
https://bugs.ruby-lang.org/issues/7803

Author: sawa (Tsuyoshi Sawada)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 


In the RDoc documentation for `Array#&`, it does not mention whether the order of the elements in the returned array preserves the order in the receiver. There is a question raised regarding this point in stackoverflow:

    http://stackoverflow.com/questions/14764135/is-order-preserved-in-arrays-when-intersection-is-done

and it mentions that that is included in the test for RubySpec

    https://github.com/rubyspec/rubyspec/blob/master/core/array/intersection_spec.rb#L16

so it looks like that is taken for granted, but it is not guaranteed. If it is indeed a feature, then that should be written in the document. If not, (meaning the order might not be preserved in a future implementation), then that should also be mentioned in the document as a warning. The documentation for `Array#-` makes that point clear:

    Array Difference---Returns a new array that is a copy of the original array, removing any items that ...

so, perhaps the docmentation for `Array#&` should be written along the same line.


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