progress and some refactoring

util/defaultmap.js

@@ -0,0 +1,18 @@
+
+export class DefaultMap {
+  constructor(defaultValue, ...rest) {
+    this.defaultValue = defaultValue;
+    this.m = new Map(rest);
+  }
+  getdefault(key, addToMapping = false) {
+    return this.m.get(key) || (() => {
+      const val = this.defaultValue(key);
+      if (addToMapping)
+        this.m.set(key, val);
+      return val;
+    })();
+  }
+  entries() {
+    return this.m.entries();
+  }
+}

util/pretty.js

@@ -0,0 +1,7 @@
+import { inspect } from 'node:util';
+
+
+export function pretty(obj) {
+  return inspect(obj, { colors: true, depth: null });
+}
+

util/util.js

@@ -0,0 +1,31 @@
+
+// re-inventing the wheel:
+export function deepEqual(a, b) {
+  if (a === b) return true; // <- shallow equality and primitives
+  if (typeof a !== 'object' || typeof b !== 'object' || a === null || b === null) {
+    return false;
+  }
+  if (Array.isArray(a) && Array.isArray(b)) {
+    if (a.length !== b.length) return false;
+    for (let i = 0; i < a.length; i++) {
+      if (!deepEqual(a[i], b[i])) return false;
+    }
+    return true;
+  }
+  const keysA = Object.keys(a);
+  const keysB = Object.keys(b);
+  if (keysA.length !== keysB.length) return false;
+  for (let key of keysA) {
+    if (!keysB.includes(key) || !deepEqual(a[key], b[key])) {
+      return false;
+    }
+  }
+  return true;
+}
+
+// zip two arrays
+export function zip(a, b) {
+  return a.map((k, i) => [k, b[i]]);
+}
+
+