update book code

eBook/examples/chapter_13/even/even/even.go

@@ -0,0 +1,10 @@
+// even.go
+package even
+
+func Even(i int) bool {		// Exported function
+	return i%2 == 0
+}
+
+func Odd(i int) bool {		// Exported function
+	return i%2 != 0
+}

eBook/examples/chapter_13/even/even/oddeven_test.go

@@ -0,0 +1,27 @@
+// oddeven_test.go
+package even
+
+import "testing"
+	
+func TestEven(t *testing.T) {
+	if !Even(10) {
+		t.Log(" 10 must be even!")
+		t.Fail()
+	}
+	if Even(7) {
+		t.Log(" 7 is not even!")
+		t.Fail()
+	}
+
+}
+
+func TestOdd(t *testing.T) {
+	if !Odd(11) {
+		t.Log(" 11 must be odd!")
+		t.Fail()
+	}
+	if Odd(10) {
+		t.Log(" 10 is not odd!")
+		t.Fail()
+	}
+}