// Homework 30, challenge: package stack. Finish the TODOs.
//
// The rule to protect: Pop on an empty stack must not crash. It returns an
// error instead.

package stack

import "errors"

// Stack is a stack of strings. Make one with New.
type Stack struct {
	// TODO: add a field that holds the items, with a lower case name.
}

// New returns an empty stack.
func New() *Stack {
	return &Stack{}
}

// Push adds v on top.
func (s *Stack) Push(v string) {
	// TODO: add v to the items.
}

// Pop removes and returns the top item, or returns an error if the stack is
// empty.
func (s *Stack) Pop() (string, error) {
	// TODO: check for an empty stack, then take the top item off.
	return "", errors.New("TODO: replace this line")
}

// Size returns the number of items.
func (s *Stack) Size() int {
	// TODO: replace this placeholder value.
	return 0
}