Simplify nth comparison when reusing transformed tokens

src/core.go

@@ -192,11 +192,12 @@ func Run(opts *Options) (int, error) {
 	}
 
 	nth := opts.Nth
+	nthRevision := 0
 	patternCache := make(map[string]*Pattern)
 	patternBuilder := func(runes []rune) *Pattern {
 		return BuildPattern(cache, patternCache,
 			opts.Fuzzy, opts.FuzzyAlgo, opts.Extended, opts.Case, opts.Normalize, forward, withPos,
-			opts.Filter == nil, nth, opts.Delimiter, runes)
+			opts.Filter == nil, nth, opts.Delimiter, nthRevision, runes)
 	}
 	inputRevision := revision{}
 	snapshotRevision := revision{}
@@ -378,6 +379,7 @@ func Run(opts *Options) (int, error) {
 						if val.nth != nil {
 							// Change nth and clear caches
 							nth = *val.nth
+							nthRevision++
 							patternCache = make(map[string]*Pattern)
 							cache.Clear()
 							inputRevision.bumpMinor()

src/item.go

@@ -8,9 +8,9 @@ import (
 
 type transformed struct {
 	// Because nth can be changed dynamically by change-nth action, we need to
-	// keep the nth value at the time of transformation.
+	// keep the revision number at the time of transformation.
-	nth    []Range
+	revision int
-	tokens []Token
+	tokens   []Token
 }
 
 // Item represents each input line. 56 bytes.

src/pattern.go

@@ -60,6 +60,7 @@ type Pattern struct {
 	cacheKey      string
 	delimiter     Delimiter
 	nth           []Range
+	revision      int
 	procFun       map[termType]algo.Algo
 	cache         *ChunkCache
 }
@@ -72,7 +73,7 @@ func init() {
 
 // BuildPattern builds Pattern object from the given arguments
 func BuildPattern(cache *ChunkCache, patternCache map[string]*Pattern, fuzzy bool, fuzzyAlgo algo.Algo, extended bool, caseMode Case, normalize bool, forward bool,
-	withPos bool, cacheable bool, nth []Range, delimiter Delimiter, runes []rune) *Pattern {
+	withPos bool, cacheable bool, nth []Range, delimiter Delimiter, revision int, runes []rune) *Pattern {
 
 	var asString string
 	if extended {
@@ -140,6 +141,7 @@ func BuildPattern(cache *ChunkCache, patternCache map[string]*Pattern, fuzzy boo
 		sortable:      sortable,
 		cacheable:     cacheable,
 		nth:           nth,
+		revision:      revision,
 		delimiter:     delimiter,
 		cache:         cache,
 		procFun:       make(map[termType]algo.Algo)}
@@ -394,23 +396,14 @@ func (p *Pattern) extendedMatch(item *Item, withPos bool, slab *util.Slab) ([]Of
 func (p *Pattern) transformInput(item *Item) []Token {
 	if item.transformed != nil {
 		transformed := *item.transformed
-		if len(transformed.nth) == len(p.nth) {
+		if transformed.revision == p.revision {
-			same := true
+			return transformed.tokens
-			for idx, rangeItem := range transformed.nth {
-				if rangeItem != p.nth[idx] {
-					same = false
-					break
-				}
-			}
-			if same {
-				return transformed.tokens
-			}
 		}
 	}
 
 	tokens := Tokenize(item.text.ToString(), p.delimiter)
 	ret := Transform(tokens, p.nth)
-	item.transformed = &transformed{p.nth, ret}
+	item.transformed = &transformed{p.revision, ret}
 	return ret
 }
 

src/pattern_test.go

@@ -68,7 +68,7 @@ func buildPattern(fuzzy bool, fuzzyAlgo algo.Algo, extended bool, caseMode Case,
 	withPos bool, cacheable bool, nth []Range, delimiter Delimiter, runes []rune) *Pattern {
 	return BuildPattern(NewChunkCache(), make(map[string]*Pattern),
 		fuzzy, fuzzyAlgo, extended, caseMode, normalize, forward,
-		withPos, cacheable, nth, delimiter, runes)
+		withPos, cacheable, nth, delimiter, 0, runes)
 }
 
 func TestExact(t *testing.T) {
@@ -135,7 +135,7 @@ func TestOrigTextAndTransformed(t *testing.T) {
 		chunk.items[0] = Item{
 			text:        util.ToChars([]byte("junegunn")),
 			origText:    &origBytes,
-			transformed: &transformed{pattern.nth, trans}}
+			transformed: &transformed{pattern.revision, trans}}
 		pattern.extended = extended
 		matches := pattern.matchChunk(&chunk, nil, slab) // No cache
 		if !(matches[0].item.text.ToString() == "junegunn" &&