interpreter.go
package interpreterimport (//"fmt""strconv""strings")const (SUM = "sum"SUB = "sub"MUL = "mul"DIV = "div")type polishNotationStack []intfunc (p *polishNotationStack) Push(s int) {*p = append(*p, s)}func (p *polishNotationStack) Pop() int {length := len(*p)if length > 0 {temp := (*p)[length-1]*p = (*p)[:length-1]return temp}return 0}func Calculate(o string) (int, error) {stack := polishNotationStack{}operators := strings.Split(o, " ")for _, operatorString := range operators {if isOperator(operatorString) {right := stack.Pop()left := stack.Pop()mathFunc := getOperationFunc(operatorString)res := mathFunc(left, right)stack.Push(res)} else {val, err := strconv.Atoi(operatorString)if err != nil {return 0, err}stack.Push(val)}}return int(stack.Pop()), nil}func isOperator(o string) bool {if o == SUM || o == SUB || o == MUL || o == DIV {return true}return false}func getOperationFunc(o string) func(a, b int) int {switch o {case SUM:return func(a, b int) int {return a + b}case SUB:return func(a, b int) int {return a - b}case MUL:return func(a, b int) int {return a * b}case DIV:return func(a, b int) int {return a / b}}return nil}
interpreter_test.go
package interpreterimport ("testing")func TestCalculate(t *testing.T) {tempOperation := "3 4 sum 2 sub"res, err := Calculate(tempOperation)if err != nil {t.Error(err)}if res != 5 {t.Errorf("Expected result not found: %d != %d\n", 5, res)}tempOperation = "5 3 sub 8 mul 4 sum 5 div"res, err = Calculate(tempOperation)if err != nil {t.Error(err)}if res != 4 {t.Errorf("Expected result not found: %d != %d\n", 4, res)}}
