strings-and-runes: added comments, output and listed in examples

examples/strings-and-runes/strings-and-runes.go

@@ -0,0 +1,73 @@
+// A Go string is a read-only slice of bytes. The language
+// and the standard library treat strings specially - as
+// containers of text encoded in [UTF-8](https://en.wikipedia.org/wiki/UTF-8).
+// In other languages, strings are made of "characters".
+// In Go, the concept of a character is called a `rune` - it's
+// an integer that represents a Unicode code point.
+// [This Go blog post](https://go.dev/blog/strings) is a good
+// introduction to the topic.
+
+package main
+
+import (
+	"fmt"
+	"unicode/utf8"
+)
+
+func main() {
+
+	// `s` is a `string` assigned a literal value
+	// representing the world "hello" in the Thai
+	// language. Go string literals are UTF-8
+	// encoded text.
+	const s = "สวัสดี"
+
+	// Since strings are equivalent to `[]byte`, this
+	// will produce the length of the raw bytes stored within.
+	fmt.Println("Len:", len(s))
+
+	// Indexing into a string produces the raw byte values at
+	// each index. This loop generates the hex values of all
+	// the bytes that constitute the code points in `s`.
+	for i := 0; i < len(s); i++ {
+		fmt.Printf("%x ", s[i])
+	}
+	fmt.Println()
+
+	// To count how many _runes_ are in a string, we can use
+	// the `utf8` package. Note that the run-time of
+	// `RuneCountInString` dependes on the size of the string,
+	// because it has to decode each UTF-8 rune sequentially.
+	// Some Thai characters are represented by multiple UTF-8
+	// code points, so the result of this count may be surprising.
+	fmt.Println("Rune count:", utf8.RuneCountInString(s))
+
+	// A `range` loop handles strings specially and decodes
+	// each `rune` along with its offset in the string.
+	for idx, runeValue := range s {
+		fmt.Printf("%#U starts at %d\n", runeValue, idx)
+	}
+
+	// We can achieve the same iteration by using the
+	// `utf8.DecodeRuneInString` function explicitly.
+	fmt.Println("\nUsing DecodeRuneInString")
+	for i, w := 0, 0; i < len(s); i += w {
+		runeValue, width := utf8.DecodeRuneInString(s[i:])
+		fmt.Printf("%#U starts at %d\n", runeValue, i)
+		w = width
+
+		// This demonstrates passing a `rune` value to a function.
+		examineRune(runeValue)
+	}
+}
+
+func examineRune(r rune) {
+
+	// Values enclosed in single quotes are _rune literals_. We
+	// can compare a `rune` value to a rune literal directly.
+	if r == 't' {
+		fmt.Println("found tee")
+	} else if r == 'ส' {
+		fmt.Println("found so sua")
+	}
+}

examples/strings-and-runes/strings-and-runes.hash

@@ -0,0 +1,2 @@
+c96321f2951af50985c648779a3a41d0b48007a7
+jDBFShEYIwP

examples/strings-and-runes/strings-and-runes.sh

@@ -0,0 +1,20 @@
+$ go run strings-and-runes.go
+Len: 18
+e0 b8 aa e0 b8 a7 e0 b8 b1 e0 b8 aa e0 b8 94 e0 b8 b5 
+Rune count: 6
+U+0E2A 'ส' starts at 0
+U+0E27 'ว' starts at 3
+U+0E31 'ั' starts at 6
+U+0E2A 'ส' starts at 9
+U+0E14 'ด' starts at 12
+U+0E35 'ี' starts at 15
+
+Using DecodeRuneInString
+U+0E2A 'ส' starts at 0
+found so sua
+U+0E27 'ว' starts at 3
+U+0E31 'ั' starts at 6
+U+0E2A 'ส' starts at 9
+found so sua
+U+0E14 'ด' starts at 12
+U+0E35 'ี' starts at 15

examples/strings-runes/strings-runes.go

@@ -1,45 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"unicode/utf8"
-)
-
-// TODO: Thai hello, vowels
-
-func main() {
-	const hello = "สวัสดี"
-	foo(hello)
-}
-
-func foo(s string) {
-	fmt.Println("Len:", len(s))
-
-	for i := 0; i < len(s); i++ {
-		fmt.Printf("%x ", s[i])
-	}
-	fmt.Println()
-
-	fmt.Println("Rune count:", utf8.RuneCountInString(s))
-
-	for idx, runeValue := range s {
-		fmt.Printf("%#U starts at %d\n", runeValue, idx)
-	}
-
-	fmt.Println("\nUsing DecodeRuneInString")
-	for i, w := 0, 0; i < len(s); i += w {
-		runeValue, width := utf8.DecodeRuneInString(s[i:])
-		fmt.Printf("%#U starts at %d\n", runeValue, i)
-		w = width
-
-		examineRune(runeValue)
-	}
-}
-
-func examineRune(r rune) {
-	if r == 't' {
-		fmt.Println("found tee")
-	} else if r == 'ส' {
-		fmt.Println("found so sua")
-	}
-}