Feature #12447: Integer#digits for extracting digits of place-value notation in any base

• Status: Closed
• Assignee: matz (Yukihiro Matsumoto)
• Target version: -

[mrkn (Kenta Murata)]

I sometimes want to extract digits of place-value notation of integer numbers.

For example:

12345.digits      #=> [5, 4, 3, 2, 1]
12345.digits(100) #=> [45, 23, 1]

One typical use case is calculating checksum digit.
I found some code extracting digits by the way like int.to_s.chars.map(&:to_i).

• https://github.com/joeljunstrom/ruby_luhn/blob/master/lib/luhn.rb#L43
• https://github.com/elitwin/check_digit/blob/master/lib/check_digit/damm.rb#L28
• https://github.com/elitwin/check_digit/blob/master/lib/check_digit/luhn.rb#L14
• https://github.com/elitwin/check_digit/blob/master/lib/check_digit/verhoeff.rb#L42

Introducing Integer#digits can reduce needless string allocation in such cases.

The patch was pushed into the repository in github.
https://github.com/mrkn/ruby/commit/5dce32d

[mrkn (Kenta Murata)]

• Related to Feature #4787: Integer#each_modulo(n) added

[mrkn (Kenta Murata)]

• Related to Feature #12116: `Fixnum#divmod`, `Bignum#divmod` with multiple arguments added

[mrkn (Kenta Murata)]

• Description updated (diff)

[mrkn (Kenta Murata)]

• Description updated (diff)

[matz (Yukihiro Matsumoto)]

Approved.

Matz.

[akr (Akira Tanaka)]

I wanted such method to encode integer in some binary format.
(I cannot remember concrete example.)
For example, pack("w") can be implementd using Integer#digits.

[mrkn (Kenta Murata)]

Summary of decision in today's Developer meeting:

• The results endian is little endian.
• Raise Math::DomainError for negative receiver.
• Return [0] for 0.

[mrkn (Kenta Murata)]

• Status changed from Open to Closed

Applied in changeset r55395.

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numeric.c: Add Integer#digits [Feature #12447] [ruby-core:75799]

[shyouhei (Shyouhei Urabe)]

• Related to Feature #16011: Digit grouping added