strings: use Go style character range comparison in ToUpper/ToLower

As noted by Brad in CL 170954 for package bytes.

Change-Id: I2772a356299e54ba5b7884d537e6649039adb9be
Reviewed-on: https://go-review.googlesource.com/c/go/+/171198
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/strings/strings.go b/src/strings/strings.go
index 5a126a7a19d88fe712cfb3c041207ad6ae7a2528..1805a14bd2b1cc13de4f14c5e67fc97771cee223 100644 (file)
--- a/src/strings/strings.go
+++ b/src/strings/strings.go
@@ -559,7 +559,7 @@ func ToUpper(s string) string {
                        isASCII = false
                        break
                }
-               hasLower = hasLower || (c >= 'a' && c <= 'z')
+               hasLower = hasLower || ('a' <= c && c <= 'z')
        }
 
        if isASCII { // optimize for ASCII-only strings.
@@ -570,7 +570,7 @@ func ToUpper(s string) string {
                b.Grow(len(s))
                for i := 0; i < len(s); i++ {
                        c := s[i]
-                       if c >= 'a' && c <= 'z' {
+                       if 'a' <= c && c <= 'z' {
                                c -= 'a' - 'A'
                        }
                        b.WriteByte(c)
@@ -589,7 +589,7 @@ func ToLower(s string) string {
                        isASCII = false
                        break
                }
-               hasUpper = hasUpper || (c >= 'A' && c <= 'Z')
+               hasUpper = hasUpper || ('A' <= c && c <= 'Z')
        }
 
        if isASCII { // optimize for ASCII-only strings.
@@ -600,7 +600,7 @@ func ToLower(s string) string {
                b.Grow(len(s))
                for i := 0; i < len(s); i++ {
                        c := s[i]
-                       if c >= 'A' && c <= 'Z' {
+                       if 'A' <= c && c <= 'Z' {
                                c += 'a' - 'A'
                        }
                        b.WriteByte(c)