Update to gobook@c6d7a22edd03e7738c38d5baa2174ff325d8d863

ch4/nonempty/main.go

@@ -0,0 +1,47 @@
+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// See page 91.
+
+//!+nonempty
+
+// Nonempty is an example of an in-place slice algorithm.
+package main
+
+import "fmt"
+
+// nonempty returns a slice holding only the non-empty strings.
+// The underlying array is modified during the call.
+func nonempty(strings []string) []string {
+	i := 0
+	for _, s := range strings {
+		if s != "" {
+			strings[i] = s
+			i++
+		}
+	}
+	return strings[:i]
+}
+
+//!-nonempty
+
+func main() {
+	//!+main
+	data := []string{"one", "", "three"}
+	fmt.Printf("%q\n", nonempty(data)) // `["one" "three"]`
+	fmt.Printf("%q\n", data)           // `["one" "three" "three"]`
+	//!-main
+}
+
+//!+alt
+func nonempty2(strings []string) []string {
+	out := strings[:0] // zero-length slice of original
+	for _, s := range strings {
+		if s != "" {
+			out = append(out, s)
+		}
+	}
+	return out
+}
+
+//!-alt