union constructor: accept interval or union

Author: victorpoughon

src/union.ts

@@ -61,9 +61,14 @@ export class Union {
     }
 }
 
-// Construct a union
+// Construct a union from a list of intervals or unions
+export function union(list: (Interval | Union)[]): Union {
+    const intervals = list.map((e) => (e instanceof Interval ? e : e.intervals)).flat();
+    return iunion(intervals);
+}
+
 // Minimum disjoint set of a list of intervals
-export function union(intervals: Interval[]): Union {
+function iunion(intervals: Interval[]): Union {
     if (intervals.length <= 1) {
         return new Union(intervals);
     }

tests/union.test.ts

@@ -16,12 +16,24 @@ function ordered(U: nsf.Union): boolean {
 
 describe("union", () => {
     it("union creation", () => {
+        // From a list of intervals
         assert.ok(ordered(nsf.union([])));
         assert.ok(ordered(nsf.union([nsf.interval(-Infinity, Infinity)])));
         assert.ok(ordered(nsf.union([nsf.interval(0, 0)])));
         assert.ok(ordered(nsf.union([nsf.interval(1, 2), nsf.interval(4, 10)])));
         assert.ok(ordered(nsf.union([nsf.interval(1, 2), nsf.interval(-10, -5)])));
         assert.ok(ordered(nsf.union([nsf.interval(1, 2), nsf.interval(-5, 5)])));
+
+        // From a list of unions
+        const a = nsf.union([nsf.interval(0, 0)]);
+        const b = nsf.union([nsf.interval(1, 2), nsf.interval(4, 10)]);
+        const c = nsf.union([nsf.interval(1, 2), nsf.interval(-10, -5)]);
+        const d = nsf.union([nsf.interval(10000, Infinity)]);
+
+        assert.ok(ordered(nsf.union([a, b, c, d])));
+
+        // Mix of intervals and unions
+        assert.ok(ordered(nsf.union([a, b, nsf.interval(5, 6), nsf.interval(-1000, -500)])));
     });
 
     it("union contains", () => {