From: "sawa (Tsuyoshi Sawada) via ruby-core" <ruby-core@...>
Date: 2023-01-19T08:59:21+00:00
Subject: [ruby-core:111903] [Ruby master Feature#13890] Allow a regexp as an argument to 'count', to count more interesting things than single characters

Issue #13890 has been updated by sawa (Tsuyoshi Sawada).





Can't overlapping be realized by putting the overlapping part within a look-ahead? Is there a use case where it cannot?



----------------------------------------

Feature #13890: Allow a regexp as an argument to 'count', to count more interesting things than single characters

https://bugs.ruby-lang.org/issues/13890#change-101324



* Author: duerst (Martin D�rst)

* Status: Open

* Priority: Normal

----------------------------------------

Currently, String#count only accepts strings, and counts all the characters in the string.



However, I have repeatedly met the situation where I wanted to count more interesting things in strings.

These 'interesting things' can easily be expressed with regular expressions.



Here is a quick-and-dirty Ruby-level implementation:



````Ruby

class String

  alias old_count count



  def count (what)

    case what

    when String

      old_count what

    when Regexp

      pos = -1

      count = 0

      count += 1 while pos = index(what, pos+1)

      count

    end

  end

end

````



Please note that the implementation counts overlapping occurrences; maybe there is room for an option like `overlap: :no`.







-- 

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