# File lib/english/porter.rb, line 100
100:     def self.stem(word)
101:       # make a copy of the given object and convert it to a string.
102:       word = word.dup.to_str
103: 
104:       return word if word.length < 3
105: 
106:       # now map initial y to Y so that the patterns never treat it as vowel
107:       word[0] = 'Y' if word[0] == yy
108: 
109:       # Step 1a
110:       if word =~ /(ss|i)es$/
111:         word = $` + $1
112:       elsif word =~ /([^s])s$/
113:         word = $` + $1
114:       end
115: 
116:       # Step 1b
117:       if word =~ /eed$/
118:         word.chop! if $` =~ MGR0
119:       elsif word =~ /(ed|ing)$/
120:         stem = $`
121:         if stem =~ VOWEL_IN_STEM
122:           word = stem
123:           case word
124:             when /(at|bl|iz)$/             then word << "e"
125:             when /([^aeiouylsz])\11$$/       then word.chop!
126:             when /^#{CC}#{V}[^aeiouwxy]$/ then word << "e"
127:           end
128:         end
129:       end
130: 
131:       if word =~ /y$/
132:         stem = $`
133:         word = stem + "i" if stem =~ VOWEL_IN_STEM
134:       end
135: 
136:       # Step 2
137:       if word =~ PORTER_STEMS_RE[0]
138:         stem = $`
139:         suffix = $1
140:         # print "stem= " + stem + "\n" + "suffix=" + suffix + "\n"
141:         if stem =~ MGR0
142:           word = stem + PORTER_STEMS[0][suffix]
143:         end
144:       end
145: 
146:       # Step 3
147:       if word =~ PORTER_STEMS_RE[1]
148:         stem = $`
149:         suffix = $1
150:         if stem =~ MGR0
151:           word = stem + PORTER_STEMS[1][suffix]
152:         end
153:       end
154: 
155:       # Step 4
156:       if word =~ PORTER_STEMS_RE[2]
157:         stem = $`
158:         if stem =~ MGR1
159:           word = stem
160:         end
161:       elsif word =~ /(s|t)(ion)$/
162:         stem = $` + $1
163:         if stem =~ MGR1
164:           word = stem
165:         end
166:       end
167: 
168:       #  Step 5
169:       if word =~ /e$/
170:         stem = $`
171:         if (stem =~ MGR1) ||
172:             (stem =~ MEQ1 && stem !~ /^#{CC}#{V}[^aeiouwxy]$/)
173:           word = stem
174:         end
175:       end
176: 
177:       if word =~ /ll$/ && word =~ MGR1
178:         word.chop!
179:       end
180: 
181:       # and turn initial Y back to y
182:       word[0] = 'y' if word[0] == YY
183: 
184:       word
185:     end