Misc #19131: MatchData#values_at(): addressing with Range and Integer index behaves differently for the first element (entire matched string)

• Status: Open
• Assignee: -

[andrykonchin (Andrew Konchin)]

I've noticed a strange nuance and not sure whether it's intentional or not. In case it's intentional - it seems to me inconsistent.

I will illustrate it with the following example:

/(.)(.)(.)(.)/.match("abcde").values_at(-5..-1) # => ["abcd", "a", "b", "c", "d"]
/(.)(.)(.)(.)/.match("abcde").values_at(-5) # => [nil]

So with a negative index we can address the whole matched string (0 element) with a Range argument but cannot with an Integer index.

We can index with negative values only captured values:

/(.)(.)(.)(.)/.match("abcde").values_at(-4) # => ["a"]
/(.)(.)(.)(.)/.match("abcde").values_at(-3) # => ["b"]
/(.)(.)(.)(.)/.match("abcde").values_at(-2) # => ["c"]
# ...

I would expect Range and Integer arguments are handled consistently and either both allow to address the first element with negative index or both disallow it.

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ruby -v
ruby 3.1.2p20 (2022-04-12 revision 4491bb740a) [x86_64-darwin21]

[andrykonchin (Andrew Konchin)]

• Description updated (diff)

[andrykonchin (Andrew Konchin)]

• Description updated (diff)