Copy sort.Search to avoid an import

difference.go

@@ -1,7 +1,5 @@
 package intervals
 
-import "sort"
-
 // Difference returns the set of elements that are in x, but not in y.
 func (x Set[E]) Difference(y Set[E]) Set[E] {
 	return difference(x, y, nil)
@@ -40,7 +38,7 @@ func difference[E Elem[E]](x, y, out Set[E]) Set[E] {
 		r := y[0]
 		y = y[1:]
 
-		i := sort.Search(len(x), func(i int) bool { return x[i].High.Compare(r.Low) > 0 })
+		i := sortSearch(len(x), func(i int) bool { return x[i].High.Compare(r.Low) > 0 })
 
 		if !inv {
 			z = append(z, x[:i]...)
@@ -49,7 +47,7 @@ func difference[E Elem[E]](x, y, out Set[E]) Set[E] {
 		x = x[i:]
 
 	Again:
-		j := sort.Search(len(x), func(i int) bool { return x[i].Low.Compare(r.High) >= 0 })
+		j := sortSearch(len(x), func(i int) bool { return x[i].Low.Compare(r.High) >= 0 })
 
 		if j == 0 {
 			if inv {

intersection.go

@@ -1,7 +1,5 @@
 package intervals
 
-import "sort"
-
 // Intersection returns the set of elements that are in both x and y.
 func (x Set[E]) Intersection(y Set[E]) Set[E] {
 	return intersection(x, y, nil)
@@ -31,9 +29,9 @@ func intersection[E Elem[E]](x, y, out Set[E]) Set[E] {
 		r := y[0]
 		y = y[1:]
 
-		i := sort.Search(len(x), func(i int) bool { return x[i].High.Compare(r.Low) > 0 })
+		i := sortSearch(len(x), func(i int) bool { return x[i].High.Compare(r.Low) > 0 })
 		x = x[i:]
-		j := sort.Search(len(x), func(i int) bool { return x[i].Low.Compare(r.High) >= 0 })
+		j := sortSearch(len(x), func(i int) bool { return x[i].Low.Compare(r.High) >= 0 })
 
 		if j > 0 {
 			start := len(z)

intervalset.go

@@ -1,8 +1,6 @@
 // Package intervals is a library for manipulating sets of intervals.
 package intervals
 
-import "sort"
-
 // Elem is the type set containing all supported element types.
 type Elem[E any] interface {
 	Compare(E) int
@@ -114,8 +112,8 @@ func (x *Set[E]) Add(r Interval[E]) {
 func (x *Set[E]) AddRange(lo, hi E) {
 	s := *x
 
-	i := sort.Search(len(s), func(i int) bool { return s[i].Low.Compare(lo) > 0 })
-	// j := sort.Search(len(s), func(i int) bool { return s[i].High.Compare(hi) > 0 })
+	i := sortSearch(len(s), func(i int) bool { return s[i].Low.Compare(lo) > 0 })
+	// j := sortSearch(len(s), func(i int) bool { return s[i].High.Compare(hi) > 0 })
 
 	// ┌────────┬─────────────────────────────────────────┐
 	// │        │    j-1        j        i-1        i     │
@@ -145,7 +143,7 @@ func (x *Set[E]) AddRange(lo, hi E) {
 	// Optimized: j >= i-1.
 	off := max(0, i-1)
 	t := s[off:]
-	j := off + sort.Search(len(t), func(i int) bool { return t[i].High.Compare(hi) > 0 })
+	j := off + sortSearch(len(t), func(i int) bool { return t[i].High.Compare(hi) > 0 })
 
 	if i > j { // Case 1 and 2.
 		return
@@ -192,8 +190,8 @@ func (x *Set[E]) Delete(r Interval[E]) {
 func (x *Set[E]) DeleteRange(lo, hi E) {
 	s := *x
 
-	i := sort.Search(len(s), func(i int) bool { return s[i].High.Compare(lo) > 0 })
-	// j := sort.Search(len(s), func(i int) bool { return s[i].Low.Compare(hi) > 0 })
+	i := sortSearch(len(s), func(i int) bool { return s[i].High.Compare(lo) > 0 })
+	// j := sortSearch(len(s), func(i int) bool { return s[i].Low.Compare(hi) > 0 })
 
 	// ┌────────┬─────────────────────────────────────────┐
 	// │        │    j-1        j        i-1        i     │
@@ -222,7 +220,7 @@ func (x *Set[E]) DeleteRange(lo, hi E) {
 
 	// Optimized: j >= i.
 	t := s[i:]
-	j := i + sort.Search(len(t), func(i int) bool { return t[i].Low.Compare(hi) > 0 })
+	j := i + sortSearch(len(t), func(i int) bool { return t[i].Low.Compare(hi) > 0 })
 
 	if i == j { // Case 1, 2 and 3.
 		return
@@ -276,13 +274,13 @@ func (x Set[E]) Contains(r Interval[E]) bool {
 
 // ContainsOne reports whether x contains a single element v.
 func (x Set[E]) ContainsOne(v E) bool {
-	i := sort.Search(len(x), func(i int) bool { return x[i].High.Compare(v) > 0 })
+	i := sortSearch(len(x), func(i int) bool { return x[i].High.Compare(v) > 0 })
 	return i < len(x) && x[i].Low.Compare(v) <= 0
 }
 
 // ContainsRange reports whether x contains every element in range [lo, hi).
 func (x Set[E]) ContainsRange(lo, hi E) bool {
-	i := sort.Search(len(x), func(i int) bool { return x[i].High.Compare(lo) > 0 })
+	i := sortSearch(len(x), func(i int) bool { return x[i].High.Compare(lo) > 0 })
 	return i < len(x) && x[i].Low.Compare(lo) <= 0 && x[i].High.Compare(hi) >= 0 && lo.Compare(hi) < 0
 }
 
@@ -314,3 +312,21 @@ func (x Set[E]) Extent() Interval[E] {
 		High: x[len(x)-1].High,
 	}
 }
+
+// sortSearch is like sort.Search, avoiding an import.
+func sortSearch(n int, f func(int) bool) int {
+	// Define f(-1) == false and f(n) == true.
+	// Invariant: f(i-1) == false, f(j) == true.
+	i, j := 0, n
+	for i < j {
+		h := int(uint(i+j) >> 1) // avoid overflow when computing h
+		// i ≤ h < j
+		if !f(h) {
+			i = h + 1 // preserves f(i-1) == false
+		} else {
+			j = h // preserves f(j) == true
+		}
+	}
+	// i == j, f(i-1) == false, and f(j) (= f(i)) == true  =>  answer is i.
+	return i
+}

issubsetof.go

@@ -1,7 +1,5 @@
 package intervals
 
-import "sort"
-
 // IsSubsetOf reports whether elements in x are all in y.
 func (x Set[E]) IsSubsetOf(y Set[E]) bool {
 	inv := false
@@ -25,7 +23,7 @@ func (x Set[E]) IsSubsetOf(y Set[E]) bool {
 		y = y[1:]
 
 		if inv {
-			i := sort.Search(len(x), func(i int) bool { return x[i].High.Compare(r.Low) > 0 })
+			i := sortSearch(len(x), func(i int) bool { return x[i].High.Compare(r.Low) > 0 })
 			x = x[i:]
 
 			if len(x) == 0 || x[0].Low.Compare(r.Low) > 0 || x[0].High.Compare(r.High) < 0 {
@@ -39,7 +37,7 @@ func (x Set[E]) IsSubsetOf(y Set[E]) bool {
 			return false
 		}
 
-		j := sort.Search(len(x), func(i int) bool { return x[i].Low.Compare(r.High) >= 0 })
+		j := sortSearch(len(x), func(i int) bool { return x[i].Low.Compare(r.High) >= 0 })
 
 		if j > 0 {
 			if x[j-1].High.Compare(r.High) > 0 {

overlap.go

@@ -1,7 +1,5 @@
 package intervals
 
-import "sort"
-
 // Overlaps reports whether the intersection of x and y is not empty.
 func (x Set[E]) Overlaps(y Set[E]) bool {
 	for {
@@ -20,9 +18,9 @@ func (x Set[E]) Overlaps(y Set[E]) bool {
 		r := y[0]
 		y = y[1:]
 
-		i := sort.Search(len(x), func(i int) bool { return x[i].High.Compare(r.Low) > 0 })
+		i := sortSearch(len(x), func(i int) bool { return x[i].High.Compare(r.Low) > 0 })
 		x = x[i:]
-		j := sort.Search(len(x), func(i int) bool { return x[i].Low.Compare(r.High) >= 0 })
+		j := sortSearch(len(x), func(i int) bool { return x[i].Low.Compare(r.High) >= 0 })
 
 		if j > 0 {
 			return true

symdiff.go

@@ -1,7 +1,5 @@
 package intervals
 
-import "sort"
-
 // SymmetricDifference returns the set of elements that are in one of x and y,
 // but not in both.
 func (x Set[E]) SymmetricDifference(y Set[E]) Set[E] {
@@ -34,12 +32,12 @@ func symmetricDifference[E Elem[E]](x, y, out Set[E]) Set[E] {
 		r := y[0]
 		y = y[1:]
 
-		i := sort.Search(len(x), func(i int) bool { return x[i].High.Compare(r.Low) > 0 })
+		i := sortSearch(len(x), func(i int) bool { return x[i].High.Compare(r.Low) > 0 })
 		z = appendIntervals(z, x[:i]...)
 		x = x[i:]
 
 	Again:
-		j := sort.Search(len(x), func(i int) bool { return x[i].Low.Compare(r.High) >= 0 })
+		j := sortSearch(len(x), func(i int) bool { return x[i].Low.Compare(r.High) >= 0 })
 
 		if j == 0 {
 			z = appendInterval(z, r)

union.go

@@ -1,7 +1,5 @@
 package intervals
 
-import "sort"
-
 // Union returns the set of elements that are in either x, or y, or both.
 func (x Set[E]) Union(y Set[E]) Set[E] {
 	return union(x, y, nil)
@@ -31,7 +29,7 @@ func union[E Elem[E]](x, y, out Set[E]) Set[E] {
 		r := y[0]
 		y = y[1:]
 
-		i := sort.Search(len(x), func(i int) bool { return x[i].High.Compare(r.Low) >= 0 })
+		i := sortSearch(len(x), func(i int) bool { return x[i].High.Compare(r.Low) >= 0 })
 		z = append(z, x[:i]...)
 		x = x[i:]
 
@@ -40,7 +38,7 @@ func union[E Elem[E]](x, y, out Set[E]) Set[E] {
 		}
 
 	Again:
-		j := sort.Search(len(x), func(i int) bool { return x[i].High.Compare(r.High) > 0 })
+		j := sortSearch(len(x), func(i int) bool { return x[i].High.Compare(r.High) > 0 })
 		x = x[j:]
 
 		if len(x) != 0 && x[0].Low.Compare(r.High) <= 0 {