add new Union methods

Author: victorpoughon

README.md

@@ -153,7 +153,7 @@ $$
 To construct a union, use the `nsf.union()` function:
 
 ```typescript
-nsf.union(intervals: Interval[]) : Union
+function union(list: (Interval | Union)[]): Union
 ```
 
 Union class member functions:
@@ -163,6 +163,9 @@ class Union {
     isEmpty(): boolean;
     isFull(): boolean;
     isFinite(): boolean;
+    isSingle(): boolean;
+    equalsSingle(lower: number, upper: number): boolean;
+    count(): number;
     lower(): number;
     upper(): number;
     contains(value: number): boolean;
@@ -262,3 +265,4 @@ function complement(A: Union | Interval): Union;
 ## Future improvements
 
 -   Support multiple rounding modes
+-   Improve unit test coverage

src/union.ts

@@ -24,6 +24,18 @@ export class Union {
         );
     }
 
+    public isSingle(): boolean {
+        return this.intervals.length === 1;
+    }
+
+    public equalsSingle(lower: number, upper: number) {
+        return this.isSingle() && this.intervals[0].lo === lower && this.intervals[0].hi === upper;
+    }
+
+    public count(): number {
+        return this.intervals.length;
+    }
+
     public lower(): number {
         if (this.isEmpty()) return Infinity;
         return this.intervals[0].lo;

tests/union.test.ts

@@ -14,8 +14,8 @@ function ordered(U: nsf.Union): boolean {
     return true;
 }
 
-describe("union", () => {
-    it("union creation", () => {
+describe("Union", () => {
+    it("Union creation", () => {
         // From a list of intervals
         assert.ok(ordered(nsf.union([])));
         assert.ok(ordered(nsf.union([nsf.interval(-Infinity, Infinity)])));
@@ -36,7 +36,7 @@ describe("union", () => {
         assert.ok(ordered(nsf.union([a, b, nsf.interval(5, 6), nsf.interval(-1000, -500)])));
     });
 
-    it("union contains", () => {
+    it("Union.contains()", () => {
         const a = nsf.union([nsf.interval(0, 10), nsf.interval(50, 60)]);
         assert.ok(!nsf.EMPTY.contains(0));
         assert.ok(a.contains(0));
@@ -50,7 +50,7 @@ describe("union", () => {
         assert.ok(!a.contains(15));
     });
 
-    it("union subset", () => {
+    it("Union.subset()", () => {
         const a = nsf.union([nsf.interval(0, 10), nsf.interval(50, 60)]);
         assert.ok(a.subset(nsf.single(0, 100)));
         assert.ok(a.subset(nsf.FULL));
@@ -59,15 +59,15 @@ describe("union", () => {
         assert.ok(nsf.EMPTY.subset(nsf.FULL));
     });
 
-    it("union superset", () => {
+    it("Union.superset()", () => {
         const a = nsf.union([nsf.interval(0, 10), nsf.interval(50, 60)]);
         assert.ok(a.superset(nsf.single(0, 1)));
         assert.ok(a.superset(nsf.EMPTY));
         assert.ok(a.superset(nsf.union([nsf.interval(2, 3), nsf.interval(5, 6)])));
         assert.ok(nsf.FULL.superset(nsf.EMPTY));
     });
 
-    it("union isFinite", () => {
+    it("union.isFinite()", () => {
         assert.ok(nsf.EMPTY.isFinite());
         assert.ok(nsf.single(0, 1).isFinite());
         assert.ok(nsf.union([nsf.single(0, 1), nsf.single(4, 5)]).isFinite());
@@ -90,4 +90,20 @@ describe("union", () => {
 
         assert.deepEqual(nsf.FULL.width(), Infinity);
     });
+
+    it("Union.count()", () => {
+        assert.deepEqual(nsf.EMPTY.count(), 0);
+        assert.deepEqual(nsf.single(0, 0).count(), 1);
+        assert.deepEqual(nsf.FULL.count(), 1);
+        assert.deepEqual(nsf.union([nsf.single(0, 0), nsf.single(1, 2)]).count(), 2);
+    });
+
+    it("Union.isSingle()", () => {
+        assert.deepEqual(nsf.EMPTY.isSingle(), false);
+        assert.deepEqual(nsf.FULL.isSingle(), true);
+        assert.deepEqual(nsf.single(0, 0).isSingle(), true);
+        assert.deepEqual(nsf.single(0, 1).isSingle(), true);
+        assert.deepEqual(nsf.single(-1, 1).isSingle(), true);
+        assert.deepEqual(nsf.union([nsf.single(0, 1), nsf.single(10, 11)]).isSingle(), false);
+    });
 });