Add exercises for chapter 22

Author: marijnh

11_async.md

@@ -370,6 +370,8 @@ Such a function no longer, like a regular JavaScript function, runs from start t
 
 For most asynchronous code, this notation is more convenient than directly using promises. You do still need an understanding of promises, since in many cases you still interact with them directly. But when wiring them together, `async` functions are generally more pleasant to write than chains of `then` calls.
 
+{{id generator}}
+
 ## Generators
 
 {{index "async function"}}

code/solutions/22_1_prime_numbers.js

@@ -0,0 +1,22 @@
+function* primes() {
+  for (let n = 2;; n++) {
+    let skip = false;
+    for (let d = 2; d < n; d++) {
+      if (n % d == 0) {
+        skip = true;
+        break;
+      }
+    }
+    if (!skip) yield n;
+  }
+}
+
+function measurePrimes() {
+  let iter = primes(), t0 = Date.now();
+  for (let i = 0; i < 10000; i++) {
+    iter.next();
+  }
+  console.log(`Took ${Date.now() - t0}ms`);
+}
+
+measurePrimes();

code/solutions/22_2_faster_prime_numbers.js

@@ -0,0 +1,28 @@
+function* primes() {
+  let found = [];
+  for (let n = 2;; n++) {
+    let skip = false, root = Math.sqrt(n);
+    for (let prev of found) {
+      if (prev > root) {
+        break;
+      } else if (n % prev == 0) {
+        skip = true;
+        break;
+      }
+    }
+    if (!skip) {
+      found.push(n);
+      yield n;
+    }
+  }
+}
+
+function measurePrimes() {
+  let iter = primes(), t0 = Date.now();
+  for (let i = 0; i < 10000; i++) {
+    iter.next();
+  }
+  console.log(`Took ${Date.now() - t0}ms`);
+}
+
+measurePrimes();

src/chapter_info.mjs

@@ -86,7 +86,8 @@ for (let file of fs.readdirSync(".").sort()) {
     number: "1[3]",
     type: "js",
     code: "async function locateScalpel(nest) {\n  // Your code here.\n}\n\nfunction locateScalpel2(nest) {\n  // Your code here.\n}\n\nlocateScalpel(bigOak).then(console.log);\n// → Butcher Shop",
-    solution: "async function locateScalpel(nest) {\n  let current = nest.name;\n  for (;;) {\n    let next = await anyStorage(nest, current, \"scalpel\");\n    if (next == current) return current;\n    current = next;\n  }\n}\n\nfunction locateScalpel2(nest) {\n  function loop(current) {\n    return anyStorage(nest, current, \"scalpel\").then(next => {\n      if (next == current) return current;\n      else return loop(next);\n    });\n  }\n  return loop(nest.name);\n}\n\nlocateScalpel(bigOak).then(console.log);\n// → Butcher's Shop\nlocateScalpel2(bigOak).then(console.log);\n// → Butcher's Shop"
+    solution: "async function locateScalpel(nest) {\n  let current = nest.name;\n  for (;;) {\n    let next = await anyStorage(nest, current, \"scalpel\");\n    if (next == current) return current;\n    current = next;\n  }\n}\n\nfunction locateScalpel2(nest) {\n  function loop(current) {\n    return anyStorage(nest, current, \"scalpel\").then(next => {\n      if (next == current) return current;\n      else return loop(next);\n    });\n  }\n  return loop(nest.name);\n}\n\nlocateScalpel(bigOak).then(console.log);\n// → Butcher's Shop\nlocateScalpel2(bigOak).then(console.log);\n// → Butcher's Shop",
+    goto: "https://eloquentjavascript.net/3rd_edition/code/#11.1"
   })
   if (chapter.number == 20) chapter.exercises = [
     {name: "Search tool",
@@ -134,29 +135,46 @@ for (let file of fs.readdirSync(".").sort()) {
 output.push({
   title: "JavaScript and Performance",
   number: 22,
-  start_code: "<!-- This chapter exists in the paper book, not in the online version -->\n\n<script>\n  runLayout(forceDirected_simple, treeGraph(4, 4));\n</script>\n",
+  start_code: "<!-- This chapter exists in the paper book, not in the online version -->\n\n<script>\n  runLayout(forceDirected_simple, gridGraph(12));\n</script>\n",
   include: ["code/draw_layout.js", "code/chapter/22_fast.js"],
   exercises: [
-    {name: "Pathfinding",
-     file: "code/solutions/22_1_pathfinding.js",
+    {name: "Prime numbers",
+     file: "code/solutions/22_1_prime_numbers.js",
      number: 1,
      type: "js",
+     code: "function* primes() {\n  for (let n = 2;; n++) {\n    // ...\n  }\n}\n\nfunction measurePrimes() {\n  // ...\n}\n\nmeasurePrimes();\n",
+     solution: fs.readFileSync("code/solutions/22_1_prime_numbers.js", "utf8")
+    },
+    {name: "Faster prime numbers",
+     file: "code/solutions/22_2_faster_prime_numbers.js",
+     number: 2,
+     type: "js",
+     code: "function* primes() {\n  for (let n = 2;; n++) {\n    // ...\n  }\n}\n\nfunction measurePrimes() {\n  // ...\n}\n\nmeasurePrimes();\n",
+     solution: fs.readFileSync("code/solutions/22_2_faster_prime_numbers.js", "utf8"),
+    },
+    {name: "Pathfinding [3rd ed]",
+     file: "code/solutions/22_1_pathfinding.js",
+     number: "1[3]",
+     type: "js",
      code: "function findPath(a, b) {\n  // Your code here...\n}\n\nlet graph = treeGraph(4, 4);\nlet root = graph[0], leaf = graph[graph.length - 1];\nconsole.log(findPath(root, leaf).length);\n// → 4\n\nleaf.connect(root);\nconsole.log(findPath(root, leaf).length);\n// → 2\n",
-     solution: fs.readFileSync("code/solutions/22_1_pathfinding.js", "utf8")
+     solution: fs.readFileSync("code/solutions/22_1_pathfinding.js", "utf8"),
+     goto: "https://eloquentjavascript.net/3rd_edition/code/#22.1"
     },
-    {name: "Timing",
+    {name: "Timing [3rd ed]",
      file: "code/solutions/22_2_timing.js",
-     number: 2,
+     number: "2[3]",
      type: "js",
      code: "",
-     solution: fs.readFileSync("code/solutions/22_2_timing.js", "utf8")
+     solution: fs.readFileSync("code/solutions/22_2_timing.js", "utf8"),
+     goto: "https://eloquentjavascript.net/3rd_edition/code/#22.2"
     },
-    {name: "Optimizing",
+    {name: "Optimizing [3rd ed]",
      file: "code/solutions/22_3_optimizing.js",
-     number: 3,
+     number: "3[3]",
      type: "js",
      code: "",
-     solution: fs.readFileSync("code/solutions/22_3_optimizing.js", "utf8")
+     solution: fs.readFileSync("code/solutions/22_3_optimizing.js", "utf8"),
+     goto: "https://eloquentjavascript.net/3rd_edition/code/#22.3"
     }
   ]
 });

src/client/code.mjs

@@ -100,10 +100,12 @@ class CodeSandbox {
       if (chapter.start_code) code += "\n\n" + chapter.start_code
       this.setEditorState(code, {include: chapter.include})
       visible = "box"
-    } else if (value == "11.1[3]") {
-      document.location = "https://eloquentjavascript.net/3rd_edition/code/#11.1"
     } else {
       let exercise = findExercise(value, chapter)
+      if (exercise.goto) {
+        document.location = exercise.goto
+        return
+      }
       this.setEditorState(exercise.code, {
         include: chapter.include,
         solution: exercise.solution,