DocBook documentation stub added

[stg.git] / doc / help / xslt / webhelp / template / content / search / stemmers / en_stemmer.js

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+// Porter stemmer in Javascript. Few comments, but it's easy to follow against the rules in the original
+// paper, in
+//
+//  Porter, 1980, An algorithm for suffix stripping, Program, Vol. 14,
+//  no. 3, pp 130-137,
+//
+// see also http://www.tartarus.org/~martin/PorterStemmer
+
+// Release 1 be 'andargor', Jul 2004
+// Release 2 (substantially revised) by Christopher McKenzie, Aug 2009
+
+
+var stemmer = (function(){
+       var step2list = {
+                       "ational" : "ate",
+                       "tional" : "tion",
+                       "enci" : "ence",
+                       "anci" : "ance",
+                       "izer" : "ize",
+                       "bli" : "ble",
+                       "alli" : "al",
+                       "entli" : "ent",
+                       "eli" : "e",
+                       "ousli" : "ous",
+                       "ization" : "ize",
+                       "ation" : "ate",
+                       "ator" : "ate",
+                       "alism" : "al",
+                       "iveness" : "ive",
+                       "fulness" : "ful",
+                       "ousness" : "ous",
+                       "aliti" : "al",
+                       "iviti" : "ive",
+                       "biliti" : "ble",
+                       "logi" : "log"
+               },
+
+               step3list = {
+                       "icate" : "ic",
+                       "ative" : "",
+                       "alize" : "al",
+                       "iciti" : "ic",
+                       "ical" : "ic",
+                       "ful" : "",
+                       "ness" : ""
+               },
+
+               c = "[^aeiou]",          // consonant
+               v = "[aeiouy]",          // vowel
+               C = c + "[^aeiouy]*",    // consonant sequence
+               V = v + "[aeiou]*",      // vowel sequence
+
+               mgr0 = "^(" + C + ")?" + V + C,               // [C]VC... is m>0
+               meq1 = "^(" + C + ")?" + V + C + "(" + V + ")?$",  // [C]VC[V] is m=1
+               mgr1 = "^(" + C + ")?" + V + C + V + C,       // [C]VCVC... is m>1
+               s_v = "^(" + C + ")?" + v;                   // vowel in stem
+
+       return function (w) {
+               var     stem,
+                       suffix,
+                       firstch,
+                       re,
+                       re2,
+                       re3,
+                       re4,
+                       origword = w;
+
+               if (w.length < 3) { return w; }
+
+               firstch = w.substr(0,1);
+               if (firstch == "y") {
+                       w = firstch.toUpperCase() + w.substr(1);
+               }
+
+               // Step 1a
+               re = /^(.+?)(ss|i)es$/;
+               re2 = /^(.+?)([^s])s$/;
+
+               if (re.test(w)) { w = w.replace(re,"$1$2"); }
+               else if (re2.test(w)) { w = w.replace(re2,"$1$2"); }
+
+               // Step 1b
+               re = /^(.+?)eed$/;
+               re2 = /^(.+?)(ed|ing)$/;
+               if (re.test(w)) {
+                       var fp = re.exec(w);
+                       re = new RegExp(mgr0);
+                       if (re.test(fp[1])) {
+                               re = /.$/;
+                               w = w.replace(re,"");
+                       }
+               } else if (re2.test(w)) {
+                       var fp = re2.exec(w);
+                       stem = fp[1];
+                       re2 = new RegExp(s_v);
+                       if (re2.test(stem)) {
+                               w = stem;
+                               re2 = /(at|bl|iz)$/;
+                               re3 = new RegExp("([^aeiouylsz])\\1$");
+                               re4 = new RegExp("^" + C + v + "[^aeiouwxy]$");
+                               if (re2.test(w)) {      w = w + "e"; }
+                               else if (re3.test(w)) { re = /.$/; w = w.replace(re,""); }
+                               else if (re4.test(w)) { w = w + "e"; }
+                       }
+               }
+
+               // Step 1c
+               re = /^(.+?)y$/;
+               if (re.test(w)) {
+                       var fp = re.exec(w);
+                       stem = fp[1];
+                       re = new RegExp(s_v);
+                       if (re.test(stem)) { w = stem + "i"; }
+               }
+
+               // Step 2
+               re = /^(.+?)(ational|tional|enci|anci|izer|bli|alli|entli|eli|ousli|ization|ation|ator|alism|iveness|fulness|ousness|aliti|iviti|biliti|logi)$/;
+               if (re.test(w)) {
+                       var fp = re.exec(w);
+                       stem = fp[1];
+                       suffix = fp[2];
+                       re = new RegExp(mgr0);
+                       if (re.test(stem)) {
+                               w = stem + step2list[suffix];
+                       }
+               }
+
+               // Step 3
+               re = /^(.+?)(icate|ative|alize|iciti|ical|ful|ness)$/;
+               if (re.test(w)) {
+                       var fp = re.exec(w);
+                       stem = fp[1];
+                       suffix = fp[2];
+                       re = new RegExp(mgr0);
+                       if (re.test(stem)) {
+                               w = stem + step3list[suffix];
+                       }
+               }
+
+               // Step 4
+               re = /^(.+?)(al|ance|ence|er|ic|able|ible|ant|ement|ment|ent|ou|ism|ate|iti|ous|ive|ize)$/;
+               re2 = /^(.+?)(s|t)(ion)$/;
+               if (re.test(w)) {
+                       var fp = re.exec(w);
+                       stem = fp[1];
+                       re = new RegExp(mgr1);
+                       if (re.test(stem)) {
+                               w = stem;
+                       }
+               } else if (re2.test(w)) {
+                       var fp = re2.exec(w);
+                       stem = fp[1] + fp[2];
+                       re2 = new RegExp(mgr1);
+                       if (re2.test(stem)) {
+                               w = stem;
+                       }
+               }
+
+               // Step 5
+               re = /^(.+?)e$/;
+               if (re.test(w)) {
+                       var fp = re.exec(w);
+                       stem = fp[1];
+                       re = new RegExp(mgr1);
+                       re2 = new RegExp(meq1);
+                       re3 = new RegExp("^" + C + v + "[^aeiouwxy]$");
+                       if (re.test(stem) || (re2.test(stem) && !(re3.test(stem)))) {
+                               w = stem;
+                       }
+               }
+
+               re = /ll$/;
+               re2 = new RegExp(mgr1);
+               if (re.test(w) && re2.test(w)) {
+                       re = /.$/;
+                       w = w.replace(re,"");
+               }
+
+               // and turn initial Y back to y
+
+               if (firstch == "y") {
+                       w = firstch.toLowerCase() + w.substr(1);
+               }
+
+               return w;
+       }
+})();
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