v1.16.12

Added: * slicesx: ** Last ** LastIndex
2026-07-14 03:02:22 -04:00
parent c9f3e7a639
commit b85d328311
5 changed files with 284 additions and 2 deletions
@@ -0,0 +1,4 @@
+/*
+Package slicesx aims to extend functionality of the stdlib [slices] module.
+*/
+package slicesx
@@ -0,0 +1,43 @@
+package slicesx
+
+/*
+Last returns the last item/element in slice s.
+
+e will be the nil/zero value of the slice element type
+if the slice length is 0.
+*/
+func Last[S ~[]E, E any](s S) (e E) {
+
+	var idx int = LastIndex(s)
+
+	if idx < 0 {
+		return
+	}
+
+	e = s[idx]
+
+	return
+}
+
+/*
+LastIndex returns the index of the last element in slice s.
+
+If s is empty, idx will be -1.
+If s is nil, idx will be -2.
+*/
+func LastIndex[S ~[]E, E any](s S) (idx int) {
+
+	var l int = len(s)
+
+	idx = -2
+	if s != nil {
+		idx++
+	}
+	if l == 0 {
+		return
+	}
+
+	idx = l - 1
+
+	return
+}
@@ -0,0 +1,235 @@
+package slicesx
+
+import (
+	"testing"
+)
+
+func TestLast(t *testing.T) {
+
+	var v any
+	var e any
+	var intSl []int
+	var strSl []string
+	var boolSl []bool
+	var anySl []any
+
+	/*
+		int
+	*/
+	// nil
+	v = Last(intSl)
+	e = 0
+	if v != e {
+		t.Errorf("%T %#v, expected %T %#v", v, v, e, e)
+	}
+	// empty
+	intSl = make([]int, 0)
+	v = Last(intSl)
+	if v != e { // still expect 0
+		t.Errorf("%T %#v, expected %T %#v", v, v, e, e)
+	}
+	// populated
+	intSl = []int{0, 1, 2, 3}
+	v = Last(intSl)
+	e = 3
+	if v != e {
+		t.Errorf("%T %#v, expected %T %#v", v, v, e, e)
+	}
+
+	/*
+		string
+	*/
+	// nil
+	v = Last(strSl)
+	e = ""
+	if v != e {
+		t.Errorf("%T %#v, expected %T %#v", v, v, e, e)
+	}
+	// empty
+	strSl = make([]string, 0)
+	v = Last(strSl)
+	if v != e { // still expect ""
+		t.Errorf("%T %#v, expected %T %#v", v, v, e, e)
+	}
+	// populated
+	strSl = []string{"a", "b", "c"}
+	v = Last(strSl)
+	e = "c"
+	if v != e {
+		t.Errorf("%T %#v, expected %T %#v", v, v, e, e)
+	}
+
+	/*
+		bool
+	*/
+	// nil
+	v = Last(boolSl)
+	e = false
+	if v != e {
+		t.Errorf("%T %#v, expected %T %#v", v, v, e, e)
+	}
+	// empty
+	boolSl = make([]bool, 0)
+	v = Last(boolSl)
+	if v != e { // still expect false
+		t.Errorf("%T %#v, expected %T %#v", v, v, e, e)
+	}
+	// populated
+	boolSl = []bool{true, false, true, false, true}
+	v = Last(boolSl)
+	e = true
+	if v != e {
+		t.Errorf("%T %#v, expected %T %#v", v, v, e, e)
+	}
+
+	/*
+		any/interface{}
+	*/
+	// nil
+	v = Last(anySl)
+	e = nil
+	if v != e {
+		t.Errorf("%T %#v, expected %T %#v", v, v, e, e)
+	}
+	// empty
+	anySl = make([]any, 0)
+	v = Last(anySl)
+	if v != e { // still expect nil
+		t.Errorf("%T %#v, expected %T %#v", v, v, e, e)
+	}
+	// populated
+	anySl = []any{3, true, "foo", "bar"}
+	v = Last(anySl)
+	e = "bar"
+	if v != e {
+		t.Errorf("%T %#v, expected %T %#v", v, v, e, e)
+	}
+}
+
+/*
+	this test only runs in Go 1.26+;
+	which lets you new() on values instead of just types.
+
+	commented out until req bumps to 1.26+ in go.mod.
+*/
+/*
+func TestLastPtr(t *testing.T) {
+
+	var v any
+	var i *int
+	var s *string
+	var b *bool
+	var ptrIntSl []*int
+	var ptrStrSl []*string
+	var ptrBoolSl []*bool
+
+
+	//
+	//	int
+	//
+	// nil
+	v = Last(ptrIntSl)
+	i = nil
+	if v != i {
+		t.Errorf("%T %#v, expected %T %#v", v, v, i, i)
+	}
+	// empty
+	ptrIntSl = make([]*int, 0)
+	v = Last(ptrIntSl)
+	if v != i { // still expect nil
+		t.Errorf("%T %#v, expected %T %#v", v, v, i, i)
+	}
+	// populated
+	ptrIntSl = []*int{new(0), new(1), new(2), new(3)}
+	v = Last(ptrIntSl)
+	i = ptrIntSl[len(ptrIntSl)-1]
+	if v != i {
+		t.Errorf("%T %#v, expected %T %#v", v, v, i, i)
+	}
+
+	//
+	//	string
+	//
+	// nil
+	v = Last(ptrStrSl)
+	if v != s {
+		t.Errorf("%T %#v, expected %T %#v", v, v, s, s)
+	}
+	// empty
+	ptrStrSl = make([]*string, 0)
+	v = Last(ptrStrSl)
+	if v != s { // still expect nil
+		t.Errorf("%T %#v, expected %T %#v", v, v, s, s)
+	}
+	// populated
+	ptrStrSl = []*string{new("a"), new("b"), new("c")}
+	v = Last(ptrStrSl)
+	s = ptrStrSl[len(ptrStrSl)-1]
+	if v != s {
+		t.Errorf("%T %#v, expected %T %#v", v, v, s, s)
+	}
+
+	//
+	//	bool
+	//
+	// nil
+	v = Last(ptrBoolSl)
+	if v != b {
+		t.Errorf("%T %#v, expected %T %#v", v, v, b, b)
+	}
+	// empty
+	ptrBoolSl = make([]*bool, 0)
+	v = Last(ptrBoolSl)
+	if v != b { // still expect nil
+		t.Errorf("%T %#v, expected %T %#v", v, v, b, b)
+	}
+	// populated
+	ptrBoolSl = []*bool{new(true), new(false), new(true), new(false), new(true)}
+	v = Last(ptrBoolSl)
+	b = ptrBoolSl[len(ptrBoolSl)-1]
+	if v != b {
+		t.Errorf("%T %#v, expected %T %#v", v, v, b, b)
+	}
+}
+*/
+
+func TestLastIndex(t *testing.T) {
+
+	var e int
+	var v int
+	var s []string
+
+	e = -2
+	v = LastIndex(s)
+	if e != v {
+		t.Errorf("Got %d, expected %d", v, e)
+	}
+
+	e = -1
+	s = make([]string, 0)
+	v = LastIndex(s)
+	if e != v {
+		t.Errorf("Got %d, expected %d", v, e)
+	}
+
+	e = 0
+	s = []string{"a"}
+	v = LastIndex(s)
+	if e != v {
+		t.Errorf("Got %d, expected %d", v, e)
+	}
+
+	e = 1
+	s = []string{"a", "b"}
+	v = LastIndex(s)
+	if e != v {
+		t.Errorf("Got %d, expected %d", v, e)
+	}
+
+	e = 2
+	s = []string{"a", "b", "c"}
+	v = LastIndex(s)
+	if e != v {
+		t.Errorf("Got %d, expected %d", v, e)
+	}
+}
@@ -636,7 +636,7 @@ pre.rouge .gs {
 <div class="details">
 <span id="author" class="author">Brent Saner</span><br>
 <span id="email" class="email"><a href="mailto:bts@square-r00t.net">bts@square-r00t.net</a></span><br>
-<span id="revdate">Last rendered 2026-07-13 19:17:39 -0400</span>
+<span id="revdate">Last rendered 2026-07-14 03:02:23 -0400</span>
 </div>
 <div id="toc" class="toc2">
 <div id="toctitle">Table of Contents</div>
@@ -6,7 +6,7 @@

 <span id="author" class="author">Brent Saner</span>  
 <span id="email" class="email"><bts@square-r00t.net></span>  
-<span id="revdate">Last rendered 2026-07-13 19:17:43 -0400</span>
+<span id="revdate">Last rendered 2026-07-14 03:02:27 -0400</span>

 </div>