Class: IndexedSearch::Match::AmericanSoundex

Inherits:
Base
  • Object
show all
Defined in:
lib/indexed_search/match/american_soundex.rb

Overview

Does the “american soundex” variation of the soundex algorithm comparison to find words that sound similar. Only works well for English.

Also supports keys longer than 4 characters, and is more tolerant of unicode characters in a way that’s somewhat similar to how MySQL’s SOUNDEX() function works…

Uses an american_soundex column to store a soundex value with each entry in the IndexedSearch::Word model. TODO: ideally non-ascii letters should be normalized to similar ascii ones if they can…

Constant Summary collapse

MAP = 
{
  'a' => '0', 'e' => '0', 'i' => '0', 'o' => '0', 'u' => '0',
  'b' => '1', 'f' => '1', 'p' => '1', 'v' => '1',
  'c' => '2', 'g' => '2', 'j' => '2', 'k' => '2', 'q' => '2', 's' => '2', 'x' => '2', 'z' => '2',
  'd' => '3', 't' => '3',
  'l' => '4',
  'm' => '5', 'n' => '5',
  'r' => '6'
}

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Base

#find, find_attributes, #initialize, match_against_term?, #results, #term_matches, #term_non_matches

Constructor Details

This class inherits a constructor from IndexedSearch::Match::Base

Class Method Details

.make_index_value(term) ⇒ Object

see: en.wikipedia.org/wiki/Soundex#Rules our exception is of course the length, and some limited unicode tolerance



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# File 'lib/indexed_search/match/american_soundex.rb', line 56

def self.make_index_value(term)
  idx = 0
  idx += 1 until term[idx] =~ /\A\p{Alpha}\z/  || idx >= term.size
  return nil if idx >= term.size
  value = UnicodeUtils.simple_upcase(term[idx])
  return value if max_length == 1
  last_code = MAP[term[idx]]
  while idx < term.size do
    idx += 1
    code = MAP[term[idx]]
    if ! code.nil? && code != last_code
      value += code if code != '0'
      return value if value.size >= max_length
      last_code = code
    end
  end
  value.ljust(4, '0')
end

Instance Method Details

#scope ⇒ Object 



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# File 'lib/indexed_search/match/american_soundex.rb', line 34

def scope
  @scope.where(self.class.matcher_attribute => term_map.keys)
end

#term_map ⇒ Object 



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# File 'lib/indexed_search/match/american_soundex.rb', line 38

def term_map
  @term_map ||= Hash.new { |hash,key| hash[key] = [] }.tap do |map|
    term_matches.each { |term| map[self.class.make_index_value(term)] << term }
  end
end