strings: make parameters names less confusing

Using 'sep' as parameter name for strings functions that take a
separator argument is fine, but for functions like Index or Count that
look for a substring it's better to use 'substr' (like Contains
already does).

Fixes #19039

Change-Id: Idd557409c8fea64ce830ab0e3fec37d3d56a79f0
Reviewed-on: https://go-review.googlesource.com/36874
Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/strings/strings.go

@@ -72,21 +72,21 @@ func hashStrRev(sep string) (uint32, uint32) {
 	return hash, pow
 }
 
-// Count counts the number of non-overlapping instances of sep in s.
-// If sep is an empty string, Count returns 1 + the number of Unicode code points in s.
-func Count(s, sep string) int {
+// Count counts the number of non-overlapping instances of substr in s.
+// If substr is an empty string, Count returns 1 + the number of Unicode code points in s.
+func Count(s, substr string) int {
 	n := 0
 	// special case
-	if len(sep) == 0 {
+	if len(substr) == 0 {
 		return utf8.RuneCountInString(s) + 1
 	}
 	for {
-		i := Index(s, sep)
+		i := Index(s, substr)
 		if i == -1 {
 			return n
 		}
 		n++
-		s = s[i+len(sep):]
+		s = s[i+len(substr):]
 	}
 }
 
@@ -105,16 +105,16 @@ func ContainsRune(s string, r rune) bool {
 	return IndexRune(s, r) >= 0
 }
 
-// LastIndex returns the index of the last instance of sep in s, or -1 if sep is not present in s.
-func LastIndex(s, sep string) int {
-	n := len(sep)
+// LastIndex returns the index of the last instance of substr in s, or -1 if substr is not present in s.
+func LastIndex(s, substr string) int {
+	n := len(substr)
 	switch {
 	case n == 0:
 		return len(s)
 	case n == 1:
-		return LastIndexByte(s, sep[0])
+		return LastIndexByte(s, substr[0])
 	case n == len(s):
-		if sep == s {
+		if substr == s {
 			return 0
 		}
 		return -1
@@ -122,20 +122,20 @@ func LastIndex(s, sep string) int {
 		return -1
 	}
 	// Rabin-Karp search from the end of the string
-	hashsep, pow := hashStrRev(sep)
+	hashss, pow := hashStrRev(substr)
 	last := len(s) - n
 	var h uint32
 	for i := len(s) - 1; i >= last; i-- {
 		h = h*primeRK + uint32(s[i])
 	}
-	if h == hashsep && s[last:] == sep {
+	if h == hashss && s[last:] == substr {
 		return last
 	}
 	for i := last - 1; i >= 0; i-- {
 		h *= primeRK
 		h += uint32(s[i])
 		h -= pow * uint32(s[i+n])
-		if h == hashsep && s[i:i+n] == sep {
+		if h == hashss && s[i:i+n] == substr {
 			return i
 		}
 	}

src/strings/strings_amd64.go

@@ -21,27 +21,27 @@ func init() {
 	}
 }
 
-// Index returns the index of the first instance of sep in s, or -1 if sep is not present in s.
-func Index(s, sep string) int {
-	n := len(sep)
+// Index returns the index of the first instance of substr in s, or -1 if substr is not present in s.
+func Index(s, substr string) int {
+	n := len(substr)
 	switch {
 	case n == 0:
 		return 0
 	case n == 1:
-		return IndexByte(s, sep[0])
+		return IndexByte(s, substr[0])
 	case n == len(s):
-		if sep == s {
+		if substr == s {
 			return 0
 		}
 		return -1
 	case n > len(s):
 		return -1
 	case n <= shortStringLen:
-		// Use brute force when s and sep both are small
+		// Use brute force when s and substr both are small
 		if len(s) <= 64 {
-			return indexShortStr(s, sep)
+			return indexShortStr(s, substr)
 		}
-		c := sep[0]
+		c := substr[0]
 		i := 0
 		t := s[:len(s)-n+1]
 		fails := 0
@@ -55,7 +55,7 @@ func Index(s, sep string) int {
 				}
 				i += o
 			}
-			if s[i:i+n] == sep {
+			if s[i:i+n] == substr {
 				return i
 			}
 			fails++
@@ -64,7 +64,7 @@ func Index(s, sep string) int {
 			// Too many means more that 1 error per 8 characters.
 			// Allow some errors in the beginning.
 			if fails > (i+16)/8 {
-				r := indexShortStr(s[i:], sep)
+				r := indexShortStr(s[i:], substr)
 				if r >= 0 {
 					return r + i
 				}
@@ -74,12 +74,12 @@ func Index(s, sep string) int {
 		return -1
 	}
 	// Rabin-Karp search
-	hashsep, pow := hashStr(sep)
+	hashss, pow := hashStr(substr)
 	var h uint32
 	for i := 0; i < n; i++ {
 		h = h*primeRK + uint32(s[i])
 	}
-	if h == hashsep && s[:n] == sep {
+	if h == hashss && s[:n] == substr {
 		return 0
 	}
 	for i := n; i < len(s); {
@@ -87,7 +87,7 @@ func Index(s, sep string) int {
 		h += uint32(s[i])
 		h -= pow * uint32(s[i-n])
 		i++
-		if h == hashsep && s[i-n:i] == sep {
+		if h == hashss && s[i-n:i] == substr {
 			return i - n
 		}
 	}

src/strings/strings_generic.go

@@ -9,16 +9,16 @@ package strings
 // TODO: implements short string optimization on non amd64 platforms
 // and get rid of strings_amd64.go
 
-// Index returns the index of the first instance of sep in s, or -1 if sep is not present in s.
-func Index(s, sep string) int {
-	n := len(sep)
+// Index returns the index of the first instance of substr in s, or -1 if substr is not present in s.
+func Index(s, substr string) int {
+	n := len(substr)
 	switch {
 	case n == 0:
 		return 0
 	case n == 1:
-		return IndexByte(s, sep[0])
+		return IndexByte(s, substr[0])
 	case n == len(s):
-		if sep == s {
+		if substr == s {
 			return 0
 		}
 		return -1
@@ -26,12 +26,12 @@ func Index(s, sep string) int {
 		return -1
 	}
 	// Rabin-Karp search
-	hashsep, pow := hashStr(sep)
+	hashss, pow := hashStr(substr)
 	var h uint32
 	for i := 0; i < n; i++ {
 		h = h*primeRK + uint32(s[i])
 	}
-	if h == hashsep && s[:n] == sep {
+	if h == hashss && s[:n] == substr {
 		return 0
 	}
 	for i := n; i < len(s); {
@@ -39,7 +39,7 @@ func Index(s, sep string) int {
 		h += uint32(s[i])
 		h -= pow * uint32(s[i-n])
 		i++
-		if h == hashsep && s[i-n:i] == sep {
+		if h == hashss && s[i-n:i] == substr {
 			return i - n
 		}
 	}

src/strings/strings_s390x.go

@@ -24,27 +24,27 @@ func init() {
 	}
 }
 
-// Index returns the index of the first instance of sep in s, or -1 if sep is not present in s.
-func Index(s, sep string) int {
-	n := len(sep)
+// Index returns the index of the first instance of substr in s, or -1 if substr is not present in s.
+func Index(s, substr string) int {
+	n := len(substr)
 	switch {
 	case n == 0:
 		return 0
 	case n == 1:
-		return IndexByte(s, sep[0])
+		return IndexByte(s, substr[0])
 	case n == len(s):
-		if sep == s {
+		if substr == s {
 			return 0
 		}
 		return -1
 	case n > len(s):
 		return -1
 	case n <= shortStringLen:
-		// Use brute force when s and sep both are small
+		// Use brute force when s and substr both are small
 		if len(s) <= 64 {
-			return indexShortStr(s, sep)
+			return indexShortStr(s, substr)
 		}
-		c := sep[0]
+		c := substr[0]
 		i := 0
 		t := s[:len(s)-n+1]
 		fails := 0
@@ -58,7 +58,7 @@ func Index(s, sep string) int {
 				}
 				i += o
 			}
-			if s[i:i+n] == sep {
+			if s[i:i+n] == substr {
 				return i
 			}
 			fails++
@@ -67,7 +67,7 @@ func Index(s, sep string) int {
 			// Too many means more that 1 error per 8 characters.
 			// Allow some errors in the beginning.
 			if fails > (i+16)/8 {
-				r := indexShortStr(s[i:], sep)
+				r := indexShortStr(s[i:], substr)
 				if r >= 0 {
 					return r + i
 				}
@@ -77,12 +77,12 @@ func Index(s, sep string) int {
 		return -1
 	}
 	// Rabin-Karp search
-	hashsep, pow := hashStr(sep)
+	hashss, pow := hashStr(substr)
 	var h uint32
 	for i := 0; i < n; i++ {
 		h = h*primeRK + uint32(s[i])
 	}
-	if h == hashsep && s[:n] == sep {
+	if h == hashss && s[:n] == substr {
 		return 0
 	}
 	for i := n; i < len(s); {
@@ -90,7 +90,7 @@ func Index(s, sep string) int {
 		h += uint32(s[i])
 		h -= pow * uint32(s[i-n])
 		i++
-		if h == hashsep && s[i-n:i] == sep {
+		if h == hashss && s[i-n:i] == substr {
 			return i - n
 		}
 	}