Stack of arbitrary data

stack.go

package stack                                                                                                       

//Stack Object to store the items in the order of pushed..
type Stack struct {                                       
        elems []interface{}                               
        top   int                                         
}                                                         

//NewStack will return a Stack object - on which you can perform
//Push, Pop, Peek, Size operations                              
func NewStack() Stack {                                         
        return Stack{make([]interface{}, 0, 50), -1}            
}                                                               

//Push () pushes a data item onto the stack
func (s *Stack) Push(val interface{}) {    
        if s != nil {                      
                s.elems = append(s.elems, val)
                s.top++                       
        }                                     
        return                                
}                                             

//Pop removes and returns the most recently pushed item from the Stack
func (s *Stack) Pop() (val interface{}, ok bool) {                    
        if s == nil {                                                 
                return nil, false                                     
        }
        if s.top >= 0 {
                val := s.elems[s.top]
                s.elems = s.elems[:s.top]
                s.top--
                return val, true
        }
        return nil, false
}

//Peek just returns the most recently pushed item from the Stack
func (s *Stack) Peek() (val interface{}, ok bool) {
        if s == nil {
                return nil, false
        }
        if s.top >= 0 {
                val := s.elems[s.top]
                return val, true
        }
        return nil, false
}

//Size returns the number of elements on the Stack
func (s *Stack) Size() (size int, ok bool) {
        if s == nil {
                return 0, false
        }
        return s.top + 1, true
}