update book code

eBook/exercises/chapter_10/stack_struct.go

@@ -0,0 +1,59 @@
+// stack_struct.go
+package main
+
+import (
+	"fmt"
+	"strconv"
+)
+
+const LIMIT = 4
+type Stack struct {
+	ix	   int		// first free position, so data[ix] == 0
+	data   [LIMIT]int
+}
+
+func main() {
+	st1 := new(Stack)
+	fmt.Printf("%v\n", st1)
+	st1.Push(3)
+	fmt.Printf("%v\n", st1)
+	st1.Push(7)
+	fmt.Printf("%v\n", st1)
+	st1.Push(10)
+	fmt.Printf("%v\n", st1)
+	st1.Push(99)
+	fmt.Printf("%v\n", st1)
+	p := st1.Pop()
+	fmt.Printf("Popped %d\n", p)
+	fmt.Printf("%v\n", st1)
+	p = st1.Pop()
+	fmt.Printf("Popped %d\n", p)
+	fmt.Printf("%v\n", st1)
+	p = st1.Pop()
+	fmt.Printf("Popped %d\n", p)
+	fmt.Printf("%v\n", st1)
+	p = st1.Pop()
+	fmt.Printf("Popped %d\n", p)
+	fmt.Printf("%v\n", st1)
+}
+
+func (st *Stack) Push(n int) {
+	if (st.ix + 1 > LIMIT) {
+		return	// stack is full!
+	}
+	st.data[st.ix] = n
+	st.ix++
+}
+
+func (st *Stack) Pop() int {
+	st.ix--
+	return st.data[st.ix]
+}
+
+func (st Stack) String() string {
+	str := ""
+	for ix:=0; ix<st.ix; ix++ {
+		str += "[" + strconv.Itoa(ix) + ":" + strconv.Itoa(st.data[ix]) + "] "
+	}
+	return str
+}