Added set mockup

set.go

@@ -0,0 +1,56 @@
+package discrete
+
+// On one hand, using an interface{} as a key works on some levels.
+// On the other hand, from experience, I can say that working with interface{} is a pain
+// so I don't like it in an API. An alternate idea is to make Set an interface with a method that allows you to GRAB a map[interface{}]struct{} from
+// the implementation, but that adds a lot of calls and needless operations, making the library slower
+type Set map[interface{}]struct{}
+
+var flag struct{} = struct{}{}
+
+func (s1 Set) Union(s2 Set) Set {
+	
+	for el := range s2 {
+		s1[el] = flag
+	}
+	
+	return s2
+}
+
+func (s1 Set) Intersection(s2 Set) (out Set) {
+	// Iterate over the smaller set
+	if len(s1) > len(s2) {
+		s1,s2 = s2,s1
+	} //Q: Should this just be an if-else? Style-wise I like the swap, not sure if it's performance heavy
+	
+	out = make(map[interface{}]struct{}, len(s1))
+	
+	for el := range s1 {
+		if s2[el] == flag {
+			out[el] = flag
+		}
+	}
+	
+	return out
+}
+
+func (s1 Set) Diff(s2 Set) Set {
+	// Usually modifying an element being iterated over is a no-no, but go copies the argument to range
+	// so this is safe
+	for el := range s1 {
+		if s2[el] == flag {
+			delete(s1, el)
+		}
+	}
+	
+	return s1
+}
+
+// Are Add/Remove necessary?
+func (s1 *Set) Add(element interface{}) {
+	(*s1)[element] = flag
+}
+
+func (s1 *Set) Remove(element interface{}) {
+	delete(*s1, element)
+}