diff --git a/difference.go b/difference.go
index 69be237..3bf0b15 100644
--- a/difference.go
+++ b/difference.go
@@ -62,17 +62,17 @@ func difference[E Elem[E]](x, y, out Set[E]) Set[E] {
 		switch lo := x[0].Low; lo.Compare(r.Low) {
 		case -1:
 			if !inv {
-				z = append(z, Interval[E]{lo, r.Low})
+				z = append(z, Range(lo, r.Low))
 			}
 		case +1:
 			if inv {
-				z = append(z, Interval[E]{r.Low, lo})
+				z = append(z, Range(r.Low, lo))
 			}
 		}
 
 		if inv {
 			for i := 0; i < j-1; i++ {
-				z = append(z, Interval[E]{x[i].High, x[i+1].Low})
+				z = append(z, Range(x[i].High, x[i+1].Low))
 			}
 		}
 
@@ -82,7 +82,7 @@ func difference[E Elem[E]](x, y, out Set[E]) Set[E] {
 		switch hi.Compare(r.High) {
 		case -1:
 			if inv {
-				z = append(z, Interval[E]{hi, r.High})
+				z = append(z, Range(hi, r.High))
 			}
 		case +1:
 			r.Low, r.High = r.High, hi
diff --git a/intervalset.go b/intervalset.go
index 9a3dfdd..18c4625 100644
--- a/intervalset.go
+++ b/intervalset.go
@@ -29,7 +29,7 @@ type Interval[E Elem[E]] struct {
 //
 // If v is the maximum value of E, One returns an invalid Interval.
 func One[E Enum[E]](v E) Interval[E] {
-	return Interval[E]{v, v.Next()}
+	return Range(v, v.Next())
 }
 
 // Range returns an Interval of range [lo, hi).
@@ -290,8 +290,5 @@ func (x Set[E]) Extent() Interval[E] {
 		return Interval[E]{}
 	}
 
-	return Interval[E]{
-		Low:  x[0].Low,
-		High: x[len(x)-1].High,
-	}
+	return Range(x[0].Low, x[len(x)-1].High)
 }
diff --git a/intervalset_test.go b/intervalset_test.go
index 72d051f..a2f9bc9 100644
--- a/intervalset_test.go
+++ b/intervalset_test.go
@@ -204,7 +204,7 @@ func TestExtent(t *testing.T) {
 	}{
 		{
 			Set[E]{{1, 3}, {5, 7}}.Extent(),
-			Interval[E]{1, 7},
+			Range[E](1, 7),
 		},
 		{
 			Set[E]{}.Extent(),
diff --git a/symdiff.go b/symdiff.go
index 8bfffd6..89ecc4e 100644
--- a/symdiff.go
+++ b/symdiff.go
@@ -48,13 +48,13 @@ func symmetricDifference[E Elem[E]](x, y, out Set[E]) Set[E] {
 
 		switch lo := x[0].Low; lo.Compare(r.Low) {
 		case -1:
-			z = appendInterval(z, Interval[E]{lo, r.Low})
+			z = appendInterval(z, Range(lo, r.Low))
 		case +1:
-			z = appendInterval(z, Interval[E]{r.Low, lo})
+			z = appendInterval(z, Range(r.Low, lo))
 		}
 
 		for i := 0; i < j-1; i++ {
-			z = append(z, Interval[E]{x[i].High, x[i+1].Low})
+			z = append(z, Range(x[i].High, x[i+1].Low))
 		}
 
 		hi := x[j-1].High
@@ -62,7 +62,7 @@ func symmetricDifference[E Elem[E]](x, y, out Set[E]) Set[E] {
 
 		switch hi.Compare(r.High) {
 		case -1:
-			z = append(z, Interval[E]{hi, r.High})
+			z = append(z, Range(hi, r.High))
 		case +1:
 			r.Low, r.High = r.High, hi
 			x, y = y, x