diff --git a/internal/set/doc.go b/internal/set/doc.go
deleted file mode 100644
index d803514..0000000
--- a/internal/set/doc.go
+++ /dev/null
@@ -1,21 +0,0 @@
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// Package set provides simple set data structures for uint64 and string types.
-//
-// The API for every set is:
-//	type Set(T {}) opaque
-//
-//	// Len reports the number of elements in the set.
-//	func (Set) Len() int
-//
-//	// Has reports whether an item is in the set.
-//	func (Set) Has(T) bool
-//
-//	// Set inserts the item into the set.
-//	func (Set) Set(T)
-//
-//	// Clear removes the item from the set.
-//	func (Set) Clear(T)
-package set
diff --git a/internal/set/ints.go b/internal/set/ints.go
index 0632e5a..d3d7f89 100644
--- a/internal/set/ints.go
+++ b/internal/set/ints.go
@@ -2,45 +2,30 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Package set provides simple set data structures for uint64s.
 package set
 
 import "math/bits"
 
-// Int32s represents a set of integers within the range of 0..31.
-type Int32s uint32
+// int64s represents a set of integers within the range of 0..63.
+type int64s uint64
 
-func (bs *Int32s) Len() int {
-	return bits.OnesCount32(uint32(*bs))
-}
-func (bs *Int32s) Has(n uint64) bool {
-	return uint32(*bs)&(uint32(1)<<n) > 0
-}
-func (bs *Int32s) Set(n uint64) {
-	*(*uint32)(bs) |= uint32(1) << n
-}
-func (bs *Int32s) Clear(n uint64) {
-	*(*uint32)(bs) &^= uint32(1) << n
-}
-
-// Int64s represents a set of integers within the range of 0..63.
-type Int64s uint64
-
-func (bs *Int64s) Len() int {
+func (bs *int64s) Len() int {
 	return bits.OnesCount64(uint64(*bs))
 }
-func (bs *Int64s) Has(n uint64) bool {
+func (bs *int64s) Has(n uint64) bool {
 	return uint64(*bs)&(uint64(1)<<n) > 0
 }
-func (bs *Int64s) Set(n uint64) {
+func (bs *int64s) Set(n uint64) {
 	*(*uint64)(bs) |= uint64(1) << n
 }
-func (bs *Int64s) Clear(n uint64) {
+func (bs *int64s) Clear(n uint64) {
 	*(*uint64)(bs) &^= uint64(1) << n
 }
 
 // Ints represents a set of integers within the range of 0..math.MaxUint64.
 type Ints struct {
-	lo Int64s
+	lo int64s
 	hi map[uint64]struct{}
 }
 
diff --git a/internal/set/ints_test.go b/internal/set/ints_test.go
index b370d32..9dac18b 100644
--- a/internal/set/ints_test.go
+++ b/internal/set/ints_test.go
@@ -22,75 +22,54 @@
 }
 
 func TestInts(t *testing.T) {
-	type set interface {
-		Len() int
-		Has(n uint64) bool
-		Set(n uint64)
-		Clear(n uint64)
+	ns := new(Ints)
+
+	// Check that set starts empty.
+	wantLen := 0
+	if ns.Len() != wantLen {
+		t.Errorf("init: Len() = %d, want %d", ns.Len(), wantLen)
+	}
+	for i := 0; i < maxLimit; i++ {
+		if ns.Has(uint64(i)) {
+			t.Errorf("init: Has(%d) = true, want false", i)
+		}
 	}
 
-	tests := []struct {
-		label   string
-		makeSet func() set
-		limit   int
-	}{
-		{label: "Int32s", makeSet: func() set { return new(Int32s) }, limit: 32},
-		{label: "Int64s", makeSet: func() set { return new(Int64s) }, limit: 64},
-		{label: "Ints", makeSet: func() set { return new(Ints) }, limit: maxLimit},
+	// Set some numbers.
+	for i, b := range toSet[:maxLimit] {
+		if b {
+			ns.Set(uint64(i))
+			wantLen++
+		}
 	}
 
-	for _, tt := range tests {
-		t.Run(tt.label, func(t *testing.T) {
-			ns := tt.makeSet()
+	// Check that integers were set.
+	if ns.Len() != wantLen {
+		t.Errorf("after Set: Len() = %d, want %d", ns.Len(), wantLen)
+	}
+	for i := 0; i < maxLimit; i++ {
+		if got := ns.Has(uint64(i)); got != toSet[i] {
+			t.Errorf("after Set: Has(%d) = %v, want %v", i, got, !got)
+		}
+	}
 
-			// Check that set starts empty.
-			wantLen := 0
-			if ns.Len() != wantLen {
-				t.Errorf("init: Len() = %d, want %d", ns.Len(), wantLen)
+	// Clear some numbers.
+	for i, b := range toClear[:maxLimit] {
+		if b {
+			ns.Clear(uint64(i))
+			if toSet[i] {
+				wantLen--
 			}
-			for i := 0; i < tt.limit; i++ {
-				if ns.Has(uint64(i)) {
-					t.Errorf("init: Has(%d) = true, want false", i)
-				}
-			}
+		}
+	}
 
-			// Set some numbers.
-			for i, b := range toSet[:tt.limit] {
-				if b {
-					ns.Set(uint64(i))
-					wantLen++
-				}
-			}
-
-			// Check that integers were set.
-			if ns.Len() != wantLen {
-				t.Errorf("after Set: Len() = %d, want %d", ns.Len(), wantLen)
-			}
-			for i := 0; i < tt.limit; i++ {
-				if got := ns.Has(uint64(i)); got != toSet[i] {
-					t.Errorf("after Set: Has(%d) = %v, want %v", i, got, !got)
-				}
-			}
-
-			// Clear some numbers.
-			for i, b := range toClear[:tt.limit] {
-				if b {
-					ns.Clear(uint64(i))
-					if toSet[i] {
-						wantLen--
-					}
-				}
-			}
-
-			// Check that integers were cleared.
-			if ns.Len() != wantLen {
-				t.Errorf("after Clear: Len() = %d, want %d", ns.Len(), wantLen)
-			}
-			for i := 0; i < tt.limit; i++ {
-				if got := ns.Has(uint64(i)); got != toSet[i] && !toClear[i] {
-					t.Errorf("after Clear: Has(%d) = %v, want %v", i, got, !got)
-				}
-			}
-		})
+	// Check that integers were cleared.
+	if ns.Len() != wantLen {
+		t.Errorf("after Clear: Len() = %d, want %d", ns.Len(), wantLen)
+	}
+	for i := 0; i < maxLimit; i++ {
+		if got := ns.Has(uint64(i)); got != toSet[i] && !toClear[i] {
+			t.Errorf("after Clear: Has(%d) = %v, want %v", i, got, !got)
+		}
 	}
 }
diff --git a/internal/set/strings.go b/internal/set/strings.go
deleted file mode 100644
index e81dc10..0000000
--- a/internal/set/strings.go
+++ /dev/null
@@ -1,25 +0,0 @@
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package set
-
-// Strings represents a set of strings.
-type Strings map[string]struct{}
-
-func (ss *Strings) Len() int {
-	return len(*ss)
-}
-func (ss *Strings) Has(s string) bool {
-	_, ok := (*ss)[s]
-	return ok
-}
-func (ss *Strings) Set(s string) {
-	if *ss == nil {
-		*ss = make(map[string]struct{})
-	}
-	(*ss)[s] = struct{}{}
-}
-func (ss *Strings) Clear(s string) {
-	delete(*ss, s)
-}
diff --git a/internal/set/strings_test.go b/internal/set/strings_test.go
deleted file mode 100644
index 0b99bf7..0000000
--- a/internal/set/strings_test.go
+++ /dev/null
@@ -1,63 +0,0 @@
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package set
-
-import (
-	"strconv"
-	"testing"
-)
-
-func TestStrings(t *testing.T) {
-	var ss Strings
-
-	// Check that set starts empty.
-	wantLen := 0
-	if ss.Len() != wantLen {
-		t.Errorf("init: Len() = %d, want %d", ss.Len(), wantLen)
-	}
-	for i := 0; i < maxLimit; i++ {
-		if ss.Has(strconv.Itoa(i)) {
-			t.Errorf("init: Has(%d) = true, want false", i)
-		}
-	}
-
-	// Set some strings.
-	for i, b := range toSet[:maxLimit] {
-		if b {
-			ss.Set(strconv.Itoa(i))
-			wantLen++
-		}
-	}
-
-	// Check that strings were set.
-	if ss.Len() != wantLen {
-		t.Errorf("after Set: Len() = %d, want %d", ss.Len(), wantLen)
-	}
-	for i := 0; i < maxLimit; i++ {
-		if got := ss.Has(strconv.Itoa(i)); got != toSet[i] {
-			t.Errorf("after Set: Has(%d) = %v, want %v", i, got, !got)
-		}
-	}
-
-	// Clear some strings.
-	for i, b := range toClear[:maxLimit] {
-		if b {
-			ss.Clear(strconv.Itoa(i))
-			if toSet[i] {
-				wantLen--
-			}
-		}
-	}
-
-	// Check that strings were cleared.
-	if ss.Len() != wantLen {
-		t.Errorf("after Clear: Len() = %d, want %d", ss.Len(), wantLen)
-	}
-	for i := 0; i < maxLimit; i++ {
-		if got := ss.Has(strconv.Itoa(i)); got != toSet[i] && !toClear[i] {
-			t.Errorf("after Clear: Has(%d) = %v, want %v", i, got, !got)
-		}
-	}
-}