From befd5a65c32b4780f1eb01c5b58e5ac72bc22f88 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Thu, 9 Feb 2023 18:00:04 +0530
Subject: [PATCH] A generic Set implementation

---
 tools/utils/set.go | 78 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)
 create mode 100644 tools/utils/set.go

diff --git a/tools/utils/set.go b/tools/utils/set.go
new file mode 100644
index 000000000..56b8db0d3
--- /dev/null
+++ b/tools/utils/set.go
@@ -0,0 +1,78 @@
+// License: GPLv3 Copyright: 2023, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package utils
+
+import (
+	"fmt"
+)
+
+var _ = fmt.Print
+
+type Set[T comparable] struct {
+	items map[T]struct{}
+}
+
+func (self *Set[T]) Add(val T) {
+	self.items[val] = struct{}{}
+}
+
+func (self *Set[T]) AddItems(val ...T) {
+	for _, x := range val {
+		self.items[x] = struct{}{}
+	}
+}
+
+func (self *Set[T]) Remove(val T) {
+	delete(self.items, val)
+}
+
+func (self *Set[T]) Discard(val T) {
+	delete(self.items, val)
+}
+
+func (self *Set[T]) Has(val T) bool {
+	_, ok := self.items[val]
+	return ok
+}
+
+func (self *Set[T]) Len() int {
+	return len(self.items)
+}
+
+func (self *Set[T]) ForEach(f func(T)) {
+	for x := range self.items {
+		f(x)
+	}
+}
+
+func (self *Set[T]) Iterable() map[T]struct{} {
+	return self.items
+}
+
+func (self *Set[T]) Intersect(other *Set[T]) (ans *Set[T]) {
+	if self.Len() < other.Len() {
+		ans = NewSet[T](self.Len())
+		for x := range self.items {
+			if _, ok := other.items[x]; ok {
+				ans.items[x] = struct{}{}
+			}
+		}
+	} else {
+		ans = NewSet[T](other.Len())
+		for x := range other.items {
+			if _, ok := self.items[x]; ok {
+				ans.items[x] = struct{}{}
+			}
+		}
+	}
+	return
+}
+
+func NewSet[T comparable](capacity ...int) (ans *Set[T]) {
+	if len(capacity) == 0 {
+		ans = &Set[T]{items: make(map[T]struct{}, 8)}
+	} else {
+		ans = &Set[T]{items: make(map[T]struct{}, capacity[0])}
+	}
+	return
+}