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



18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
 
# 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]
    if 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'
        if n == 0 || w[n - 1] != 'S' || !front_vowel?(w[n + 1])
          if w[n + 1, 2] == 'IA'
            metaph += 'X'
          elsif front_vowel?(w[n + 1])
            metaph += 'S'
          elsif n > 0 && w[n + 1] == 'H' && w[n - 1] == 'S'
            metaph += 'K'
          elsif w[n + 1] == 'H'
            if n == 0 && !vowel?(w[n + 2])
              metaph += 'K'
            else
              metaph += 'X'
            end
          else
            metaph += 'K'
          end
        end
      when symb == 'D'
        if w[n + 1] == 'G' && front_vowel?(w[n + 2])
          metaph += 'J'
        else
          metaph += 'T'
        end
      when symb == 'G'
        silent = (w[n + 1] == 'H' && !vowel?(w[n + 2]))
        if n > 0 && (w[n + 1] == 'N' || w[n + 1, 3] == 'NED')
          silent = true
        end
        if n > 0 && w[n - 1] == 'D' && front_vowel?(w[n + 1])
          silent = true
        end
        hard = (n > 0 && w[n - 1] == 'G')
        unless silent
          if front_vowel?(w[n + 1]) && !hard
            metaph += 'J'
          else
            metaph += 'K'
          end
        end
      when symb == 'H'
        if !(n == l - 1 || (n > 0 && VARSON[w[n - 1]]))
          metaph += 'H' if vowel?(w[n + 1])
        end
      when symb =~ /[FJLMNR]/
        metaph += symb
      when symb == 'K'
        if n > 0 && w[n - 1] != 'C'
          metaph += 'K'
        elsif n == 0
          metaph = 'K'
        end
      when symb == 'P'
        metaph += w[n + 1] == 'H' ? 'F' : 'P'
      when symb == 'Q'
        metaph += 'K'
      when symb == 'S'
        if w[n + 1, 2] =~ /I[OA]/
          metaph += 'X'
        elsif w[n + 1] == 'H'
          metaph += 'X'
        else
          metaph += 'S'
        end
      when symb == 'T'
        if w[n + 1, 2] =~ /I[OA]/
          metaph += 'X'
        elsif w[n + 1] == 'H'
          metaph += '0' if n == 0 || w[n - 1] != 'T'
        else
          metaph += 'T' if w[n + 1, 2] != 'CH'
        end
      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
  end
  metaph
end