// Copyright © 2010-12 Qtrac Ltd.

//

// This program or package and any associated files are licensed under the

// Apache License, Version 2.0 (the "License"); you may not use these files

// except in compliance with the License. You can get a copy of the License

// at: http://www.apache.org/licenses/LICENSE-2.0.

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

//

// Copied from samples for "Programming in Go", Mark Summerfield.

package stack

import "errors"

type Stack []interface{}

func (stack *Stack) Pop() (interface{}, error) {

theStack := *stack

if len(theStack) == 0 {

return nil, errors.New("can't Pop() an empty stack")

}

x := theStack[len(theStack)-1]

*stack = theStack[:len(theStack)-1]

return x, nil

}

func (stack *Stack) Push(x interface{}) {

*stack = append(*stack, x)

}

func (stack Stack) Top() (interface{}, error) {

if len(stack) == 0 {

return nil, errors.New("can't Top() an empty stack")

}

return stack[len(stack)-1], nil

}

func (stack Stack) Cap() int {

return cap(stack)

}

func (stack Stack) Len() int {

return len(stack)

}

func (stack Stack) IsEmpty() bool {

return len(stack) == 0

}