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stack.go
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stack.go
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package data
//----------------------------------------------------------------------
// This file is part of Gospel.
// Copyright (C) 2011-2023 Bernd Fix >Y<
//
// Gospel is free software: you can redistribute it and/or modify it
// under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License,
// or (at your option) any later version.
//
// Gospel is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//
// SPDX-License-Identifier: AGPL3.0-or-later
//----------------------------------------------------------------------
// Stack for generic data types.
type Stack struct {
data [](interface{}) // list of stack elements
}
// NewStack instantiates a new generic Stack object.
func NewStack() *Stack {
return &Stack{
data: make([](interface{}), 0),
}
}
// Pop last entry from stack and return it to caller.
func (s *Stack) Pop() (v interface{}) {
pos := len(s.data) - 1
v, s.data = s.data[pos], s.data[:pos]
return
}
// Push generic entry to stack.
func (s *Stack) Push(v interface{}) {
s.data = append(s.data, v)
}
// Len returns the number of elements on stack.
func (s *Stack) Len() int {
return len(s.data)
}
// Peek at the last element pushed to stack without dropping it.
func (s *Stack) Peek() (v interface{}) {
pos := len(s.data) - 1
if pos < 0 {
return nil
}
return s.data[pos]
}
// IntStack is an Integer-based Stack type and implementation.
type IntStack struct {
data []int // list of stack elements
}
// NewIntStack instantiates a new integer-based Stack object.
func NewIntStack() *IntStack {
return &IntStack{
data: make([]int, 0),
}
}
// Pop last entry from stack and return it to caller.
func (s *IntStack) Pop() (v int) {
pos := len(s.data) - 1
v, s.data = s.data[pos], s.data[:pos]
return
}
// Push entry to stack.
func (s *IntStack) Push(v int) {
s.data = append(s.data, v)
}
// Len returns the number of elements on stack.
func (s *IntStack) Len() int {
return len(s.data)
}
// Peek at the last element pushed to stack without dropping it.
func (s *IntStack) Peek() (v int) {
return s.data[len(s.data)-1]
}
// IsTop compares last element with given value.
func (s *IntStack) IsTop(v int) bool {
pos := len(s.data) - 1
if pos < 0 {
return false
}
return s.data[pos] == v
}