From: Glenn Jackman <glennj@...>
Date: 2009-08-29T01:46:01+09:00
Subject: Re: I need a string#all_indices method--is there such a thing?

At 2009-08-28 04:20AM, "timr" wrote:
>  In ruby you can use string#index as follows:
>  str = "some text"
>  str.index(/t/)
> =>5
>  
>  But what if I want to get all the indices for a regex in the string?
>  Is there an string#all_indices method?
>  
>  I wrote the following, which works, but there must be a more elegant
>  way:
>  
>  class String
>    def all_indices(regex)
>    indices = []
>    index = 0
>      while index && index < self.length #index will be nil upon first
>  match failure, otherwise quit loop when index is equal to string
>  length
>        index = self.index(regex, index)
>        if index.is_a? Numeric   #avoids getting a nil into the indices
>  array
>          indices << index
>          index +=1
>        end
>      end
>      indices
>    end
>  end
>  p "this is a test string for the ts in the worldt".all_indices(/t/)
>  p "what is up with all the twitter hype".all_indices(/w/)
>  # >> [0, 10, 13, 16, 26, 30, 36, 45]
>  # >> [0, 11, 25]

This is a bit simpler:
    class String
      def all_indices(substring)
        idx = 0
        indices = []
        loop do
          idx = index(substring, idx)
          break if idx.nil?
          indices << idx
          idx += 1
        end
        indices
      end
    end

    require 'test/unit'
    class TestAllIndices < Test::Unit::TestCase
      def test_it
        assert_equal(
          [0, 10, 13, 16, 26, 30, 36, 45],
          "this is a test string for the ts in the worldt".all_indices(/t/)
        )
        assert_equal(
          [0, 11, 25],
          "what is up with all the twitter hype".all_indices(/w/)
        )
        assert_equal(
          [12, 17, 26, 41],
          "the quick brown fox jumps over the lazy dog".all_indices('o')
        )
        assert_equal(
          [1, 3, 5],
          "bananana".all_indices('ana')
        )
      end
    end
    
-- 
Glenn Jackman
    Write a wise saying and your name will live forever. -- Anonymous