Add packages/kripke

packages/kripke/utils.ts

@@ -0,0 +1,41 @@
+const bitIsSet = (num: number, pos: number) => (num & (1 << pos)) !== 0;
+
+export function encode<T>(all: readonly T[], set: Set<T>): number {
+  let flags = 0;
+  for (let i = 0; i < all.length; i++) {
+    if (set.has(all[i] as T)) {
+      flags |= 1 << i;
+    }
+  }
+  return flags;
+}
+
+export function decode<T>(all: readonly T[], flags: number): Set<T> {
+  const total = 2 ** all.length;
+  if (flags < 0 || flags >= total) throw Error("invalid flags");
+  const decoded = new Set<T>();
+  for (let j = 0; j < all.length; j++) {
+    if (bitIsSet(flags, j)) decoded.add(all[j] as T);
+  }
+  return decoded;
+}
+
+export function* power<T>(xs: readonly T[]) {
+  const total = 2 ** xs.length;
+  for (let i = 0; i < total; i++) {
+    yield decode(xs, i);
+  }
+}
+
+export function permutations<T>(arr: readonly T[]): T[][] {
+  if (arr.length === 0) return [[]];
+  const result: T[][] = [];
+  for (let i = 0; i < arr.length; i++) {
+    const current = arr[i];
+    const remaining = [...arr.slice(0, i), ...arr.slice(i + 1)];
+    for (const perm of permutations(remaining)) {
+      result.push([current as T, ...perm]);
+    }
+  }
+  return result;
+}