Add task3 in go

Author: Holger Lösken

src/go/t3/s1.go

@@ -0,0 +1,86 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+func Calculate(input string) (float64, error) {
+	result := 0.0
+
+	if len(input) < 1 {
+		return result, nil
+	}
+
+	splitted := strings.Split(input, " ")
+
+	if isNumeric(splitted[len(splitted)-1]) {
+		return strconv.ParseFloat(splitted[len(splitted)-1], 64)
+	}
+
+	var numbers []string
+	validOperations := []string{"+", "-", "*", "/"}
+
+	for _, element := range splitted {
+		if !IsValidElement(element, validOperations) {
+			return -1, fmt.Errorf("invalid syntax")
+		}
+
+		if isNumeric(element) {
+			numbers = append(numbers, element)
+		} else {
+			number1, numbers := numbers[len(numbers)-1], numbers[:len(numbers)-1]
+			number2, numbers := numbers[len(numbers)-1], numbers[:len(numbers)-1]
+
+			op1, _ := strconv.ParseFloat(number1, 64)
+			op2, _ := strconv.ParseFloat(number2, 64)
+
+			switch element {
+			case "+":
+				result = op2 + op1
+			case "-":
+				result = op2 - op1
+			case "*":
+				result = op2 * op1
+			case "/":
+				result = op2 / op1
+			}
+
+			numbers = append(numbers, strconv.FormatFloat(result, 'E', -1, 64))
+		}
+
+
+	}
+
+	return result, nil
+}
+
+func Find(slice []string, val string) (int, error) {
+	for i, item := range slice {
+		if item == val {
+			return i, nil
+		}
+	}
+	return -1, fmt.Errorf("cannot find element '%s'", val)
+}
+
+func isNumeric(s string) bool {
+	_, err := strconv.ParseFloat(s, 64)
+	return err == nil
+}
+
+func IsValidElement(element string, validOperations []string) bool {
+	_, err := Find(validOperations, element)
+	if !isNumeric(element) && err != nil {
+		return false
+	}
+
+	return true
+}
+
+func main() {
+	r, _:= Calculate("6 3 /")
+
+	fmt.Printf("ergebnis: %v", r)
+}

src/go/t3/s1_test.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestCalculate(t *testing.T) {
+	type test struct {
+		input string
+		want float64
+	}
+
+	tests := []test{
+		{input: "2 5 +", want: 7},
+		{input: "5 3 -", want: 2},
+		{input: "4 5 *", want: 20},
+		{input: "12 4 /", want: 3},
+		{input: "", want: 0},
+		{input: "4 7-", want: -1},
+		{input: "9 8 7.5", want: 7.5},
+		{input: "4 5 6", want: 6},
+	}
+
+	for _, tc := range tests {
+		got, err := Calculate(tc.input)
+		if !reflect.DeepEqual(tc.want, got) {
+			t.Fatalf("input: %v, expected: %v, got: %v, err: %v", tc.input, tc.want, got, err)
+		}
+	}
+}