diff --git a/package.json b/package.json
index c0a0cfb..5c4724e 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,7 @@
 {
 	"type": "module",
 	"dependencies": {
-		"@inquirer/prompts": "^7.4.0"
+		"@inquirer/prompts": "^7.4.0",
+		"functional-red-black-tree": "^1.0.1"
 	}
 }
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index e968e37..26a4565 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -11,6 +11,9 @@ importers:
       '@inquirer/prompts':
         specifier: ^7.4.0
         version: 7.4.0
+      functional-red-black-tree:
+        specifier: ^1.0.1
+        version: 1.0.1
 
 packages:
 
@@ -168,6 +171,9 @@ packages:
     resolution: {integrity: sha512-hMQ4CX1p1izmuLYyZqLMO/qGNw10wSv9QDCPfzXfyFrOaCSSoRfqE1Kf1s5an66J5JZC62NewG+mK49jOCtQew==}
     engines: {node: '>=4'}
 
+  functional-red-black-tree@1.0.1:
+    resolution: {integrity: sha512-dsKNQNdj6xA3T+QlADDA7mOSlX0qiMINjn0cgr+eGHGsbSHzTabcIogz2+p/iqP1Xs6EP/sS2SbqH+brGTbq0g==}
+
   iconv-lite@0.4.24:
     resolution: {integrity: sha512-v3MXnZAcvnywkTUEZomIActle7RXXeedOR31wwl7VlyoXO4Qi9arvSenNQWne1TcRwhCL1HwLI21bEqdpj8/rA==}
     engines: {node: '>=0.10.0'}
@@ -335,6 +341,8 @@ snapshots:
       iconv-lite: 0.4.24
       tmp: 0.0.33
 
+  functional-red-black-tree@1.0.1: {}
+
   iconv-lite@0.4.24:
     dependencies:
       safer-buffer: 2.1.2
diff --git a/scripts/rbtree_bench.js b/scripts/rbtree_bench.js
new file mode 100644
index 0000000..faae879
--- /dev/null
+++ b/scripts/rbtree_bench.js
@@ -0,0 +1,88 @@
+import createTree from "functional-red-black-tree";
+
+function benchmark(N) {
+  // fastest
+  function map() {
+    let t = new Map();
+    const startTime = Date.now();
+    for (let i=0; i<N; ++i) {
+      t.set(Math.random(), Math.random());
+    }
+    const endTime = Date.now();
+    return endTime - startTime;
+  }
+  const durInPlace = map();
+  console.log("in-place:", durInPlace, "ms");
+
+  // slower by constant factor
+  function fun() {
+    let t = createTree();
+    const startTime = Date.now(); 
+    for (let i=0; i<N; ++i) {
+      t = t.insert(Math.random(), Math.random());
+    }
+    const endTime = Date.now();
+    return endTime - startTime;
+  }
+  const durFunc = fun();
+  console.log("functional:", durFunc, "ms");
+
+  // a bit slower still
+  function funNoGC() {
+    const old = new Array(N);
+    let t = createTree();
+    const startTime = Date.now(); 
+    for (let i=0; i<N; ++i) {
+      old[i] = t; // prevent garbage collection
+      t = t.insert(Math.random(), Math.random());
+    }
+    const endTime = Date.now();
+    return endTime - startTime;
+    
+  }
+  const durFuncNoGC = (N <= 1000000) ? funNoGC() : "";
+  console.log("functional (no GC):", durFuncNoGC, "ms");
+
+  // slowest (won't scale)
+  function copying() {
+    let t = new Map();
+    const startTime = Date.now();
+    for (let i=0; i<N; ++i) {
+      t = new Map(t);
+      t.set(Math.random(), Math.random());
+    }
+    const endTime = Date.now();
+    return endTime - startTime;
+  }
+  const durCopying = (N <= 20000) ? copying() : "";
+  console.log("copying:", durCopying, "ms");
+
+  // slower than slowest
+  function copyingNoGC() {
+    const old = new Array(N);
+    let t = new Map();
+    const startTime = Date.now();
+    for (let i=0; i<N; ++i) {
+      old[i] = t; // prevent garbage collection
+      t = new Map(t);
+      t.set(Math.random(), Math.random());
+    }
+    const endTime = Date.now();
+    return endTime - startTime;
+  }
+  const durCopyingNoGC = (N <= 10000) ? copyingNoGC() : "";
+  console.log("copying (no GC):", durCopyingNoGC, "ms");
+
+  return [N, durInPlace, durFunc, durFuncNoGC, durCopying, durCopyingNoGC];
+}
+
+const results = [];
+for (const N of [100, 200, 500, 1000, 2000, 5000, 10000, 20000, 50000, 100000, 200000, 500000, 1000000, 2000000, 5000000, 10000000]) {
+  console.log("N =", N);
+  results.push(benchmark(N));
+}
+
+console.log("N;in-place;functional;functional-NoGC;copying;copying-NoGC");
+for (const [N, durInPlace, durFunc, durFuncNoGC, durCopying, durCopyingNoGC] of results) {
+  console.log(`${N};${durInPlace};${durFunc};${durFuncNoGC};${durCopying};${durCopyingNoGC}`);
+}