update book code

eBook/examples/chapter_9/pattern.go

@@ -0,0 +1,35 @@
+// pattern.go
+package main
+
+import (
+	"fmt"
+	"regexp"
+	"strconv"
+)
+
+func main() {
+	searchIn := "John: 2578.34 William: 4567.23 Steve: 5632.18" // string to search
+	pat := "[0-9]+.[0-9]+"  // pattern search for in searchIn
+	
+	f := func (s string) string {
+		v, _ := strconv.ParseFloat(s, 32)
+		return strconv.FormatFloat(v * 2, 'f', 2, 32)
+	}
+	
+	if ok, _ := regexp.Match(pat, []byte(searchIn)); ok {
+		fmt.Println("Match found!")
+	}
+	
+	re, _ := regexp.Compile(pat)
+	str := re.ReplaceAllString(searchIn, "##.#") // replace pat with "##.#"
+	fmt.Println(str)
+	// using a function :
+	str2 := re.ReplaceAllStringFunc(searchIn, f) 
+	fmt.Println(str2)
+	
+}
+/* Output:
+Match found!
+John: ##.# William: ##.# Steve: ##.#
+John: 5156.68 William: 9134.46 Steve: 11264.36
+*/