Initial version - Stack.

LICENSE

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+Copyright (c) 2022 Patrick Smith
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

go.mod

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+module github.com/pat42smith/ds
+
+go 1.19
+
+require github.com/pat42smith/gotest v0.0.1

go.sum

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+github.com/pat42smith/gotest v0.0.1 h1:NaeFsxxbfcZiFkLy8ywx89W9RWKldYW71mln4TOzCzw=
+github.com/pat42smith/gotest v0.0.1/go.mod h1:0q1IE4xoC2Nm07gIOXefKF73yrAWBjq90d6RS67dEF8=

stack.go

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+// Copyright 2022 Patrick Smith
+// Use of this source code is subject to the MIT-style license in the LICENSE file.
+
+// Package ds will implement some basic data structures in Go.
+//
+// For now, only Stack is provided.
+package ds
+
+// A Stack is a simple last-in-first-out collection of items.
+type Stack[T any] struct {
+	items []T
+}
+
+// Push inserts a value into a Stack.
+func (s *Stack[T]) Push(t T) {
+	s.items = append(s.items, t)
+}
+
+// Pop removes the value that was most recently inserted into a Stack, and not yet returned by Pop.
+//
+// It returns the value that was removed.
+// Pop panics when called on an empty Stack.
+func (s *Stack[T]) Pop() T {
+	l := len(s.items)
+	t := s.items[l-1]
+	s.items = s.items[:l-1]
+	return t
+}
+
+// Len returns the number of values currently in a Stack.
+func (s Stack[T]) Len() int {
+	return len(s.items)
+}
+
+// Empty returns whether a Stack contains no values.
+func (s Stack[T]) Empty() bool {
+	return len(s.items) == 0
+}
+
+// PushMany inserts several values into a stack.
+//
+// The values are inserted in the order given, so they will be returned by Pop in the reverse order.
+func (s *Stack[T]) PushMany(ts ...T) {
+	s.items = append(s.items, ts...)
+}

stack_test.go

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+// Copyright 2022 Patrick Smith
+// Use of this source code is subject to the MIT-style license in the LICENSE file.
+
+// Package ds will implement some basic data structures in Go.
+//
+// For now, only Stack is provided.
+package ds
+
+import (
+	"testing"
+
+	"github.com/pat42smith/gotest"
+)
+
+func TestThrees(t *testing.T) {
+	var s Stack[int]
+	gotest.Expect(t, 0, s.Len())
+	gotest.Require(t, s.Empty())
+
+	for n := 0; n < 30; n += 3 {
+		s.Push(n)
+		gotest.Expect(t, n/3+1, s.Len())
+		gotest.Require(t, !s.Empty())
+
+		s.Push(n + 1)
+		gotest.Expect(t, n/3+2, s.Len())
+		gotest.Require(t, !s.Empty())
+
+		gotest.Expect(t, n+1, s.Pop())
+		gotest.Expect(t, n/3+1, s.Len())
+		gotest.Require(t, !s.Empty())
+	}
+
+	for n := 27; n >= 0; n -= 3 {
+		gotest.Expect(t, n, s.Pop())
+	}
+
+	gotest.Expect(t, 0, s.Len())
+	gotest.Require(t, s.Empty())
+	gotest.MustPanic(t, func() { s.Pop() })
+}
+
+func TestPushMany(t *testing.T) {
+	var s Stack[string]
+	s.PushMany("alpha", "beta", "gamma", "delta")
+	s.PushMany()
+	s.PushMany("un", "deux", "trois")
+	gotest.Expect(t, "trois", s.Pop())
+	gotest.Expect(t, "deux", s.Pop())
+	gotest.Expect(t, "un", s.Pop())
+	gotest.Expect(t, "delta", s.Pop())
+	gotest.Expect(t, "gamma", s.Pop())
+	gotest.Expect(t, "beta", s.Pop())
+	gotest.Expect(t, "alpha", s.Pop())
+}