From: "e8c (Viktor Reznov) via ruby-core" <ruby-core@...>
Date: 2023-01-01T10:21:38+00:00
Subject: [ruby-core:111560] [Ruby master Feature#3591] Adding Numeric#divisor? (Have working implementation)

Issue #3591 has been updated by e8c (Viktor Reznov).


matz (Yukihiro Matsumoto) wrote in #note-19:
> Is it more useful than `n % m == 0`?

Yes, statement `n .has_divisor? m` (or `m .divisor_of? n`) has 3 parts instead of 5, and gives a direct answer to the question.

The "problem": https://leetcode.com/problems/count-the-digits-that-divide-a-number/

Two solutions:

```ruby
def count_digits(n) = n.digits.count { n % _1 == 0 }

def count_digits(n) = n.digits.count { _1.divisor_of?(n) }
```
The first is shorter, but the second is clearer.



----------------------------------------
Feature #3591: Adding Numeric#divisor? (Have working implementation)
https://bugs.ruby-lang.org/issues/3591#change-100925

* Author: duckinator (Marie Markwell)
* Status: Rejected
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
* Target version: 2.6
----------------------------------------
=begin
 On the 'duckinator' branch of my fork of ruby on github, I have added Numeric#divisor?:
   num.divisor?(other)
 is the same as:
   (num % other == 0)
 
 Example usage:
   4.divisor?(2)     #=> true
   1.divisor?(2)     #=> false
   2.4.divisor?(1.2) #=> true
   2.4.divisor?(1.3) #=> false
   126.divisor?(9)   #=> true
 
 I think this would be a very nice feature to add, and would make code using the old (num % other == 0) method much cleaner and easier to understand.
 
 There is a unified diff of it: http://gist.github.com/raw/484144/07b1a6e696cd9301e658ccbc8f90dfcd4d4ef3f1/Numeric_divisor.patch
 
 The original commits can be seen here:
 http://github.com/RockerMONO/ruby/commit/f7959f964cb0bf38418904ccb5643db6b689d29c -- First attempt, only worked with Integers
 http://github.com/RockerMONO/ruby/commit/12376a6bb1c3ffbd4b470850dd758e2dcd783dda -- Second attempt, should work with anything derived from Numeric that can be used as (num % other == 0)
=end




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