Moved stuff, added Contains to sliceutils

containers/stacks.go

@@ -0,0 +1,81 @@
+package containers
+
+import (
+	"encoding/json"
+	"errors"
+)
+
+type Stack[T any] struct {
+	top    *ChainElem[T]
+	bottom *ChainElem[T]
+}
+
+// isValid checks if the stack is valid.
+func (s *Stack[T]) isValid() bool {
+	return s.top != nil &&
+		s.bottom != nil &&
+		reachable(s.top, s.bottom)
+}
+
+// IsEmpty checks if the stack is currently empty.
+func (s *Stack[T]) IsEmpty() bool {
+	return s.top == s.bottom
+}
+
+// Push adds a new element to the top of the stack.
+// It errors out if the stack is invalid.
+func (s *Stack[T]) Push(e *T) error {
+	if !s.isValid() {
+		return errors.New("stack invalid")
+	}
+	n := emptyElem[T]()
+	n.Elem = e
+	n.Next = s.top
+	s.top = n
+	return nil
+}
+
+// Pop removes the first element at the top of the stack and returns it.
+// It errors out if the stack is invalid or empty.
+func (s *Stack[T]) Pop() (*T, error) {
+	if !s.isValid() {
+		return nil, errors.New("stack invalid")
+	}
+	if s.IsEmpty() {
+		return nil, errors.New("stack empty")
+	}
+	e := s.top.Elem
+	s.top = s.top.Next
+	return e, nil
+}
+
+// Top returns the first element at the top of the stack without removing it.
+// It errors out if the stack is empty or invalid.
+func (s *Stack[T]) Top() (*T, error) {
+	if !s.isValid() {
+		return nil, errors.New("stack invalid")
+	}
+	if s.IsEmpty() {
+		return nil, errors.New("stack empty")
+	}
+	return s.top.Elem, nil
+}
+
+// MarshalJSON is used by json.Marshal to create a json representation.
+func (s *Stack[T]) MarshalJSON() ([]byte, error) {
+	if !s.isValid() {
+		return nil, errors.New("queue invalid")
+	}
+	if s.IsEmpty() {
+		return nil, errors.New("queue empty")
+	}
+
+	return json.Marshal(s.top)
+}
+func BuildStack[T any]() *Stack[T] {
+	empty := emptyElem[T]()
+	return &Stack[T]{
+		top:    empty,
+		bottom: empty,
+	}
+}