Feature #16350: ArithmeticSequence#member? can result in infinite loop

• Status: Assigned
• Assignee: mrkn (Kenta Murata)
• Target version: -
• Tags: core

[parker (Parker Finch)]

I'm not sure if this is a bug or a feature, it feels somewhere in between.

This is my first time contributing to the Ruby code, let me know what I can improve in this report!

ArithmeticSequence#member? enumerates through the sequence in order to determine if an element is included. (It just uses Enumerable#member?.) This leads to an infinite loop if the sequence is infinite and the element is not included, such as 1.step.member?(0).

I expected 1.step.member?(0) to return false.

Since ArithmeticSequences are much more constrained than regular Enumerables, the #member? method can be overridden to efficiently determine if an element is included in the sequence.

I started implementing this change (patch attached) but got a little confused when trying to handle floats. Before digging in too deeply, I wanted to check if this is a change that will be accepted.

Let me know if I should keep looking into this!

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Assigned
• Assignee set to mrkn (Kenta Murata)

[jeremyevans0 (Jeremy Evans)]

• Tracker changed from Bug to Feature
• ruby -v deleted (ruby 2.7.0dev)
• Backport deleted (2.5: UNKNOWN, 2.6: UNKNOWN)