Bug #16966: Unexpected behavior of sort method

• Status: Rejected
• Assignee: -
• Target version: -
• ruby -v: 2.7.0
• Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN

[kk (Kirill /)]

The ruby cook book from 2015 has the following example of using sort method:

[1,100,42,23,26,1000].sort {|x,y| x==42 ? 1 : x<=>y }
# => [1, 23, 26, 100, 10000, 42]

It actually returned [1, 23, 26, 42, 100, 1000].

With a different array, I get the expected result with 42 at the end:

[1,2,42,46,22,33].sort {|x,y| x==42 ? 1 : x<=>y }
# => [1, 2, 22, 33, 46, 42]

[mame (Yusuke Endoh)]

• Status changed from Open to Rejected

It is a bug of the book. Please report it to the author :-)

There is no guarantee about which x or y accepts each element. The following code will work as expected.

[1,100,42,23,26,1000].sort {|x,y| x==42 ? 1 : y==42 ? -1 : x<=>y } #=> [1, 23, 26, 100, 1000, 42]

[sawa (Tsuyoshi Sawada)]

• Description updated (diff)