Initial Commit

internal/stack/stack.go

@@ -0,0 +1,64 @@
+/*
+   AMU: Custom simple markup language
+   Copyright (C) 2021 Arsen Musayelyan
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+// Package stack implements a simple stack using go slices.
+package stack
+
+import "reflect"
+
+// Stack is a LIFO stack using slices for storage
+type Stack struct {
+	items []interface{}
+}
+
+// Create a new stack
+func New() *Stack {
+	return &Stack{}
+}
+
+// Add a value to the end of the stack
+func (s *Stack) Push(val interface{}) {
+	// Add element to slice
+	s.items = append(s.items, val)
+}
+
+// Remove the value on the end of the stack and return it.
+func (s *Stack) Pop() interface{} {
+	// Get index of last element
+	n := s.Size() - 1
+	// Get last item in slice
+	item := s.items[n]
+	// Set element to zero value
+	s.items[n] = reflect.Zero(reflect.TypeOf(item)).Interface()
+	// Remove element
+	s.items = s.items[:n]
+	return item
+}
+
+// Return value on the end of the stack without removing
+func (s *Stack) Peek() interface{} {
+	// Get index of last element
+	n := s.Size() - 1
+	// Return last element
+	return s.items[n]
+}
+
+// Get the amount of items on the stack
+func (s *Stack) Size() int {
+	return len(s.items)
+}