Improvements to Optional type

container/optional.go

@@ -1,31 +1,31 @@
 package ucontainer
 
-// Optional is an optional value.
+// Optional can either hold a value, or nothing.
 type Optional[T any] struct {
 	value T
 	exists bool
 }
 
-// Value returns the value and true if the value exists. If not, it returns the
-// last set value and false.
-func (this *Optional[T]) Value () (T, bool) {
-	return this.value, this.exists
+// O creates a new optional with the specified value.
+func O[T any] (value T) Optional[T] {
+	return Optional[T] {
+		value: value,
+		exists: true,
+	}
 }
 
-// Set sets the value.
-func (this *Optional[T]) Set (value T) {
-	this.value = value
-	this.exists = true
-}
-
-// Unset unsets the value.
-func (this *Optional[T]) Unset () {
-	var zero T
-	this.value = zero
-	this.exists = false
+// Void returns an optional with no value.
+func Void[T any] () Optional[T] {
+	return Optional[T] { }
 }
 
 // Exists returns if the value is currently set.
-func (this *Optional[T]) Exists () bool {
-	return this.exists
+func (optional Optional[T]) Exists () bool {
+	return optional.exists
+}
+
+// Value returns the value and true if the value exists. If not, it returns the
+// zero value and false.
+func (optional Optional[T]) Value () (T, bool) {
+	return optional.value, optional.exists
 }

container/set.go

@@ -3,6 +3,15 @@ package ucontainer
 // Set is a set of unique items, built on top of map.
 type Set[T comparable] map[T] struct { }
 
+// NewSet creates a new set that contains all specified items.
+func NewSet[T comparable] (items ...T) Set[T] {
+	set := make(Set[T])
+	for _, item := range items {
+		set.Add(item)
+	}
+	return set
+}
+
 // Empty returns true if there are no items in the set.
 func (set Set[T]) Empty () bool {
 	return set == nil || len(set) == 0

go.mod

@@ -1,3 +1,3 @@
 module git.tebibyte.media/sashakoshka/goutil
 
-go 1.21.0
+go 1.22.0

image/color/color.go

@@ -22,9 +22,9 @@ func ToRGBA (c color.Color) color.RGBA {
 // Premultiply applies alpha-premultiplication that colors must apply as per
 // color.Color.RGBA. This is an intrinsically lossy proccess.
 func Premultiply (ur, ug, ub, ua uint32) (r, g, b, a uint32) {
-	return (ur * a) / 0xFFFF,
-		(ug * a) / 0xFFFF,
-		(ub * a) / 0xFFFF,
+	return (ur * ua) / 0xFFFF,
+		(ug * ua) / 0xFFFF,
+		(ub * ua) / 0xFFFF,
 		ua
 }
 

image/color/color_test.go

@@ -0,0 +1,34 @@
+package ucolor
+
+import "testing"
+import "image/color"
+
+func TestTransparent (test *testing.T) {
+	if Transparent(color.NRGBA { A: 255 }) {
+		test.Fatal("false positive")
+	}
+	if !Transparent(color.NRGBA { A: 0 }) {
+		test.Fatal("false negative")
+	}
+}
+
+func TestToRGBA (test *testing.T) {
+	rgba := ToRGBA(color.NRGBA { R: 123, G: 100, B: 23, A: 230 })
+	if rgba != (color.RGBA { R: 111, G: 90, B: 20, A: 230 }) {
+		test.Fatalf("wrong value: %v", rgba)
+	}
+}
+
+func TestPremultiply (test *testing.T) {
+	r, g, b, a := Premultiply(0xFFFF, 0xFFFF, 0xFFFF, 0x8888)
+	if r != 0x8888 || g != 0x8888 || b != 0x8888 || a != 0x8888 {
+		test.Fatalf("wrong value: %08x %08x %08x %08x", r, g, b, a)
+	}
+}
+
+func TestUnpremultiply (test *testing.T) {
+	r, g, b, a := Unpremultiply(0x8888, 0x8888, 0x8888, 0x8888)
+	if r != 0xFFFF || g != 0xFFFF || b != 0xFFFF || a != 0x8888 {
+		test.Fatalf("wrong value: %08x %08x %08x %08x", r, g, b, a)
+	}
+}