update book code

eBook/exercises/chapter_7/sum_array.go

@@ -0,0 +1,39 @@
+// leaving out the length 4 in [4] uses  slice instead of an array
+// which is generally better for performance
+package main
+
+import "fmt"
+
+func main() {
+	// var a = [4]float32 {1.0,2.0,3.0,4.0}
+	var a = []float32 {1.0,2.0,3.0,4.0}
+	fmt.Printf("The sum of the array is: %f\n", Sum(a))
+	var b = []int {1, 2, 3, 4, 5}
+	sum, average := SumAndAverage(b)
+	fmt.Printf("The sum of the array is: %d, and the average is: %f", sum, average)
+}
+
+/*
+func Sum(a [4]float32) (sum float32) {
+	for _, item := range a {
+		sum += item
+	}
+	return
+}
+*/
+
+func Sum(a []float32) (sum float32) {
+	for _, item := range a {
+		sum += item
+	}
+	return
+}
+
+func SumAndAverage (a []int) (int, float32) {
+  sum := 0
+  for _, item := range a {
+    sum += item
+  }
+  return sum, float32(sum/len(a))
+}
+