Add functions to Upper/Lower case the first letter of a string

Author: tiendc

README.md

@@ -133,6 +133,7 @@ go get github.com/tiendc/gofn
   - [StringJoin / StringJoinEx / StringJoinBy](#stringjoin--stringjoinex--stringjoinby)
   - [StringLexJoin / StringLexJoinEx](#stringlexjoin--stringlexjoinex)
   - [StringWrap / StringUnwrap](#stringwrap--stringunwrap)
+  - [StringToUpper1stLetter / StringToLower1stLetter](#stringtoupper1stletter--stringtolower1stletter)
 
 **Number**
   - [ParseInt / ParseUint / ParseFloat](#parseint--parseuint--parsefloat)
@@ -1101,6 +1102,15 @@ StringUnwrap("*abc*", "*")        // "abc"
 StringUnwrapLR("[abc]", "[", "]") // "abc"
 ```
 
+#### StringToUpper1stLetter / StringToLower1stLetter
+
+Capitalizes the first letter of a string.
+
+```go
+StringToUpper1stLetter("abc")  // "Abc"
+StringToLower1stLetter("Abc")  // "abc"
+```
+
 ### Number
 ---
 

string.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"math/rand"
 	"strings"
+	"unicode"
 	"unicode/utf8"
 )
 
@@ -201,3 +202,23 @@ func StringWrapLR(s string, tokenLeft, tokenRight string) string {
 func StringUnwrapLR(s string, tokenLeft, tokenRight string) string {
 	return strings.TrimSuffix(strings.TrimPrefix(s, tokenLeft), tokenRight)
 }
+
+// StringToUpper1stLetter uppercases the first letter of the input string
+func StringToUpper1stLetter(s string) string {
+	if len(s) == 0 {
+		return s
+	}
+	runes := []rune(s)
+	runes[0] = unicode.ToUpper(runes[0])
+	return string(runes)
+}
+
+// StringToLower1stLetter lowercases the first letter of the input string
+func StringToLower1stLetter(s string) string {
+	if len(s) == 0 {
+		return s
+	}
+	runes := []rune(s)
+	runes[0] = unicode.ToLower(runes[0])
+	return string(runes)
+}

string_test.go

@@ -101,12 +101,14 @@ func Test_LinesTrimLeft(t *testing.T) {
 		  â  line-1
 		line-2 â`))
 	// Extra func test
+	// ascii cutset
 	assert.Equal(t, "\nê b â  line-1\nê line-2 â ê ", LinesTrimLeft(`
 		 a ê b â  line-1
-		  b aê line-2 â ê `, "a b\t")) // ascii cutset
+		  b aê line-2 â ê `, "a b\t"))
+	// unicode cutset
 	assert.Equal(t, "\nâ  line-1\nline-2 â ê", LinesTrimLeft(`
 		 ê â  line-1
-		 ê line-2 â ê`, "a b\tê")) // unicode cutset
+		 ê line-2 â ê`, "a b\tê"))
 }
 
 func Test_LinesTrimRight(t *testing.T) {
@@ -129,12 +131,14 @@ line-2`))
 â  line-1  â  
 line-2`))
 	// Extra func test
+	// ascii cutset
 	assert.Equal(t, "\nâ  line-1  â  ê\nline-2  ê", LinesTrimRight(`
 â  line-1  â  ê  
-line-2  ê  `, "a b\t")) // ascii cutset
+line-2  ê  `, "a b\t"))
+	// unicode cutset
 	assert.Equal(t, "\n â  line-1  â\nline-2", LinesTrimRight(`
  â  line-1  â  ê  
-line-2  ê  `, "a b\tê")) // unicode cutset
+line-2  ê  `, "a b\tê"))
 }
 
 func Test_LinesTrim(t *testing.T) {
@@ -183,3 +187,19 @@ func Test_StringUnwrap(t *testing.T) {
 	assert.Equal(t, "abc", StringUnwrapLR("[abc]", "[", "]"))
 	assert.Equal(t, " [abc", StringUnwrapLR(" [abc]", "[", "]"))
 }
+
+func Test_StringToUpper1stLetter(t *testing.T) {
+	assert.Equal(t, "", StringToUpper1stLetter(""))
+	assert.Equal(t, " abc", StringToUpper1stLetter(" abc"))
+	assert.Equal(t, "Abc", StringToUpper1stLetter("Abc"))
+	assert.Equal(t, "Abc", StringToUpper1stLetter("abc"))
+	assert.Equal(t, "Ối", StringToUpper1stLetter("ối"))
+}
+
+func Test_StringToLower1stLetter(t *testing.T) {
+	assert.Equal(t, "", StringToLower1stLetter(""))
+	assert.Equal(t, " abc", StringToLower1stLetter(" abc"))
+	assert.Equal(t, "abc", StringToLower1stLetter("abc"))
+	assert.Equal(t, "abc", StringToLower1stLetter("Abc"))
+	assert.Equal(t, "ối", StringToLower1stLetter("Ối"))
+}