Add --no-stemming flag to skip stemming

lib/config.go

@@ -3,6 +3,7 @@ package main
 type Config struct {
 	BestFirst  bool
 	Limit      int
+	NoStemming bool
 	NoStoplist bool
 	OmitQuery  bool
 	ShowScores bool

lib/document.go

@@ -64,7 +64,12 @@ func NewDocument(path string, config *Config) (*Document, error) {
 
 			if word != "" {
 				if config.NoStoplist || !inStoplist(word) {
-					termCount[stem(word)]++
+					if config.NoStemming {
+						termCount[word]++
+					} else {
+						termCount[stem(word)]++
+					}
+
 					totalWordCount++
 				}
 			}

lib/main.go

@@ -57,6 +57,7 @@ func sameFile(a, b string) bool {
 func main() {
 	bestFirstFlag := flag.Bool("best-first", false, "print best matches first")
 	limitFlag := flag.Int("limit", 0, "return at most `limit` results")
+	noStemmingFlag := flag.Bool("no-stemming", false, "don't perform stemming on words")
 	noStoplistFlag := flag.Bool("no-stoplist", false, "don't omit common words by using a stoplist")
 	omitQueryFlag := flag.Bool("omit-query", false, "don't include the query file itself in search results")
 	queryFlag := flag.String("query", "", "path to the file that results should match")
@@ -67,6 +68,7 @@ func main() {
 	config := Config{
 		BestFirst:  *bestFirstFlag,
 		Limit:      *limitFlag,
+		NoStemming: *noStemmingFlag,
 		NoStoplist: *noStoplistFlag,
 		OmitQuery:  *omitQueryFlag,
 		ShowScores: *showScoresFlag,

man/docsim.1

@@ -26,6 +26,16 @@ default (worst to best).
 .BR \-\-limit " " \fINUM\fR
 Show no more that the best NUM results.
 .TP
+.BR \-\-no\-stemming
+Don't stem words. Stemming reduces inflected words to their word stem before
+comparing documents, which maps morphologically related words to a common term
+(so "spinning", "spinner", and "spins" might all map to "spin").
+.PP
+.RS
+Stemming usually improves scoring accuracy in English, but should probably be
+disabled when searching across code or documents in other languages.
+.RE
+.TP
 .BR \-\-no\-stoplist
 Don't filter out common words, like "the" and "because".
 .TP