Class: Phonetic::Metaphone

Inherits:
Algorithm show all
Defined in:
lib/phonetic/metaphone.rb

Overview

Metaphone is a phonetic algorithm, published by Lawrence Philips in 1990, for indexing words by their English pronunciation. This class implements this algorithm.

Examples:

Phonetic::Metaphone.encode('Accola') # => 'AKKL'
Phonetic::Metaphone.encode('Nikki') # => 'NK'
Phonetic::Metaphone.encode('Wright') #=> 'RT'

See Also:

Constant Summary collapse

VOWELS = 
'AEIOU'
FRONT_VOWELS = 
'EIY'
VARSON = 
'CSPTG'

Class Method Summary collapse

Methods inherited from Algorithm

encode

Class Method Details

.encode_word(word, options = { size: 4 }) ⇒ Object

Encode word to its Metaphone code



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# File 'lib/phonetic/metaphone.rb', line 18

def self.encode_word(word, options = { size: 4 })
  code_size = options[:size] || 4
  w = word.upcase.gsub(/[^A-Z]/, '')
  return if w.empty?
  two = w[0, 2]
  w[0] = ''  if two =~ /PN|AE|KN|GN|WR/
  w[0] = 'S' if w[0] == 'X'
  w[1] = ''  if two == 'WH'
  l = w.size
  metaph = ''
  for n in 0..(l - 1)
    break unless metaph.size < code_size
    symb = w[n]
    next unless symb == 'C' || n == 0 || w[n - 1] != symb
    case
    when vowel?(symb) && n == 0
      metaph = symb
    when symb == 'B'
      metaph += symb if n != l - 1 || w[n - 1] != 'M'
    when symb == 'C'
      metaph += encode_c(w, n)
    when symb == 'D'
      metaph += encode_d(w, n)
    when symb == 'G'
      metaph += encode_g(w, n)
    when symb == 'H'
      metaph += encode_h(w, n)
    when symb =~ /[FJLMNR]/
      metaph += symb
    when symb == 'K'
      metaph += encode_k(w, n)
    when symb == 'P'
      metaph += w[n + 1] == 'H' ? 'F' : 'P'
    when symb == 'Q'
      metaph += 'K'
    when symb == 'S'
      metaph += encode_s(w, n)
    when symb == 'T'
      metaph += encode_t(w, n)
    when symb == 'V'
      metaph += 'F'
    when symb =~ /[WY]/
      metaph += symb if vowel?(w[n + 1])
    when symb == 'X'
      metaph += 'KS'
    when symb == 'Z'
      metaph += 'S'
    end
  end
  metaph
end