diff --git a/roaring/roaring.go b/roaring/roaring.go
index 0087e6fdf..2a8b6645c 100644
--- a/roaring/roaring.go
+++ b/roaring/roaring.go
@@ -1674,19 +1674,6 @@ func (c *container) clone() *container {
 	return other
 }
 
-// flipBitmap returns a new bitmap containter containing the inverse of all
-// bits in c.
-func (c *container) flipBitmap() *container {
-	other := &container{bitmap: make([]uint64, bitmapN), containerType: ContainerBitmap}
-
-	for i, bitmap := range c.bitmap {
-		other.bitmap[i] = ^bitmap
-	}
-
-	other.n = other.count()
-	return other
-}
-
 // WriteTo writes c to w.
 func (c *container) WriteTo(w io.Writer) (n int64, err error) {
 	if c.isArray() {
@@ -1812,6 +1799,43 @@ type ContainerInfo struct {
 	Pointer unsafe.Pointer // offset within the mmap
 }
 
+// flip returns a new container containing the inverse of all
+// bits in a.
+func flip(a *container) *container {
+	if a.isArray() {
+		return flipArray(a)
+	} else if a.isRun() {
+		return flipRun(a)
+	} else {
+		return flipBitmap(a)
+	}
+}
+
+func flipArray(b *container) *container {
+	// TODO: actually implement this
+	x := b.clone()
+	x.arrayToBitmap()
+	return flipBitmap(x)
+}
+
+func flipBitmap(b *container) *container {
+	other := &container{bitmap: make([]uint64, bitmapN), containerType: ContainerBitmap}
+
+	for i, bitmap := range b.bitmap {
+		other.bitmap[i] = ^bitmap
+	}
+
+	other.n = other.count()
+	return other
+}
+
+func flipRun(b *container) *container {
+	// TODO: actually implement this
+	x := b.clone()
+	x.runToBitmap()
+	return flipBitmap(x)
+}
+
 func intersectionCount(a, b *container) int {
 	if a.isArray() {
 		if b.isArray() {
@@ -2571,7 +2595,7 @@ RUNLOOP:
 func differenceRunBitmap(a, b *container) *container {
 	// If a is full, difference is the flip of b.
 	if len(a.runs) > 0 && a.runs[0].start == 0 && a.runs[0].last == 65535 {
-		return b.flipBitmap()
+		return flipBitmap(b)
 	}
 	output := &container{containerType: ContainerRun}
 	output.n = a.n
diff --git a/roaring/roaring_helpers_test.go b/roaring/roaring_helpers_test.go
index ea6d86cd9..417ac7db6 100644
--- a/roaring/roaring_helpers_test.go
+++ b/roaring/roaring_helpers_test.go
@@ -220,8 +220,11 @@ func runEvenBitsSet() []interval16 {
 
 ///////////////////////////////////////////////////////////////////////////
 
+// f is a container function taking either one or two containers as input
+// func(a *container) *container
+// func(a, b *container) *container
 type testOp struct {
-	f   func(a, b *container) *container
+	f   interface{}
 	x   string
 	y   string
 	exp string
diff --git a/roaring/roaring_internal_test.go b/roaring/roaring_internal_test.go
index dca413811..216aa7eb7 100644
--- a/roaring/roaring_internal_test.go
+++ b/roaring/roaring_internal_test.go
@@ -2020,38 +2020,6 @@ func TestXorRunRun(t *testing.T) {
 	}
 }
 
-func TestBitmapFlip(t *testing.T) {
-	c := &container{bitmap: make([]uint64, bitmapN), containerType: ContainerBitmap}
-
-	ttable := []struct {
-		original uint64
-		flipped  uint64
-	}{
-		{0x0000000000000000, 0xFFFFFFFFFFFFFFFF},
-		{0xFFFFFFFFFFFFFFFF, 0x0000000000000000},
-		{0xFFFFFFFFFFFFFFF0, 0x000000000000000F},
-		{0xFFFFFFEFFFFFFFFF, 0x0000001000000000},
-		{0x0000001000000000, 0xFFFFFFEFFFFFFFFF},
-	}
-
-	expectedN := int(65536)
-	for i, tt := range ttable {
-		c.bitmap[i] = tt.original
-		expectedN -= int(popcount(tt.original))
-	}
-
-	o := c.flipBitmap()
-
-	for i, tt := range ttable {
-		if o.bitmap[i] != tt.flipped {
-			t.Fatalf("bitmapFlip calculation. expected %v, got %v", tt.flipped, o.bitmap[i])
-		}
-	}
-	if o.n != expectedN {
-		t.Fatalf("bitmapFlip calculation. expected count %v, got %v", expectedN, o.n)
-	}
-}
-
 func TestBitmapXorRange(t *testing.T) {
 	c := &container{bitmap: make([]uint64, bitmapN), containerType: ContainerBitmap}
 	tests := []struct {
@@ -3185,12 +3153,24 @@ func TestContainerCombinations(t *testing.T) {
 		//{xor, "evenBitsSet", "outerBitsSet", ""},
 		{xor, "evenBitsSet", "oddBitsSet", "full"},
 		{xor, "evenBitsSet", "evenBitsSet", "empty"},
+
+		// flip
+		{flip, "empty", "", "full"},
+		{flip, "full", "", "empty"},
+		{flip, "firstBitSet", "", "firstBitUnset"},
+		{flip, "lastBitSet", "", "lastBitUnset"},
+		{flip, "firstBitUnset", "", "firstBitSet"},
+		{flip, "lastBitUnset", "", "lastBitSet"},
+		{flip, "innerBitsSet", "", "outerBitsSet"},
+		{flip, "outerBitsSet", "", "innerBitsSet"},
+		{flip, "oddBitsSet", "", "evenBitsSet"},
+		{flip, "evenBitsSet", "", "oddBitsSet"},
 	}
 	for _, testOp := range testOps {
 		for _, x := range containerTypes {
 			for _, y := range containerTypes {
 				desc := fmt.Sprintf("%s(%s/%s, %s/%s)", getFunctionName(testOp.f), cm[x], testOp.x, cm[y], testOp.y)
-				ret := testOp.f(cts[x][testOp.x], cts[y][testOp.y])
+				ret := runContainerFunc(testOp.f, cts[x][testOp.x], cts[y][testOp.y])
 				exp := testOp.exp
 
 				// Convert to all container types and check result.
@@ -3240,3 +3220,14 @@ func TestContainerCombinations(t *testing.T) {
 		}
 	}
 }
+
+//func getFunc(func(a, b *container) *container, m, n *container) *container {
+func runContainerFunc(f interface{}, c ...*container) *container {
+	switch f.(type) {
+	case func(*container) *container:
+		return f.(func(*container) *container)(c[0])
+	case func(*container, *container) *container:
+		return f.(func(a, b *container) *container)(c[0], c[1])
+	}
+	return nil
+}