reorganize directory and file structure

lib/util/rbtree_wrapper.js

@@ -0,0 +1,21 @@
+// Tiny wrapper around function-red-black-tree that overrides the [inspect.custom] symbol so when we print it (during debugging) we just see the (key=>value)-pairs instead of the tree structure.
+
+import createRBTree from "functional-red-black-tree";
+import { inspect } from "util";
+
+export class RBTreeWrapper {
+  constructor(tree) {
+    this.tree = tree;
+  }
+
+  static new(compareFn) {
+    return new RBTreeWrapper(createRBTree(compareFn))
+  }
+  
+  // pretty print to console
+  [inspect.custom](depth, options, inspect) {
+    const entries = [];
+    this.tree.forEach((key, val) => { entries.push(`${inspect(key)} => ${inspect(val)}`); });
+    return `RBTree(${this.tree.length}) {${entries.join(', ')}}`;
+  }
+}