stack.go

 1package rpn
 2
 3import (
 4	"fmt"
 5)
 6
 7var ErrNotEnoughValuesTmpl = "Need at least %d values on the stack to perform this operation"
 8
 9type Stack struct {
10	values []float64
11}
12
13func (s *Stack) Push(value float64) {
14	s.values = append(s.values, value)
15}
16
17func (s *Stack) Pop() (float64, error) {
18	count := s.Len()
19	if count == 0 {
20		return 0, fmt.Errorf(ErrNotEnoughValuesTmpl, 1)
21	}
22	value := s.values[count-1]
23	s.values = s.values[:count-1]
24	return value, nil
25}
26
27func (s *Stack) Pop2() (float64, float64, error) {
28	count := s.Len()
29	if count < 2 {
30		return 0, 0, fmt.Errorf(ErrNotEnoughValuesTmpl, 2)
31	}
32	a := s.values[count-1]
33	b := s.values[count-2]
34	s.values = s.values[:count-2]
35	return a, b, nil
36}
37
38func (s *Stack) Len() int {
39	return len(s.values)
40}
41
42func (s *Stack) Swap() error {
43	count := s.Len()
44	if count < 2 {
45		return fmt.Errorf(ErrNotEnoughValuesTmpl, 2)
46	}
47	a := s.values[count-1]
48	b := s.values[count-2]
49	s.values[count-1] = b
50	s.values[count-2] = a
51	return nil
52}
53
54func (s *Stack) Clear() {
55	s.values = []float64{}
56}
57
58func (s *Stack) Values() []float64 {
59	return append([]float64(nil), s.values...)
60}