Update Recursion example to demonstrate recursive closures

Fixes #389

examples/recursion/recursion.go

@@ -17,4 +17,21 @@ func fact(n int) int {
 
 func main() {
 	fmt.Println(fact(7))
+
+	// Closures can also be recursive, but this requires the
+	// closure to be declared with a typed `var` explicitly
+	// before it's defined.
+	var fib func(n int) int
+
+	fib = func(n int) int {
+		if n < 2 {
+			return n
+		}
+		return fib(n-1) + fib(n-2)
+
+		// Since `fib` was previously declared in `main`, Go
+		// knows which function to call with `fib` here.
+	}
+
+	fmt.Println(fib(7))
 }

examples/recursion/recursion.hash

@@ -1,2 +1,2 @@
-9bfb2f870007082835a3c0efaac9aa1c3bc2c15c
+55d9633a4f0fd0eac2f243b2a2ddb35ae91ed4a9
-smWim1q9ofu
+LnBMavPrkuf

examples/recursion/recursion.sh

@@ -1,2 +1,3 @@
 $ go run recursion.go 
 5040
+13

public/recursion

@@ -43,7 +43,7 @@ Here&rsquo;s a classic factorial example.</p>
             
           </td>
           <td class="code leading">
-            <a href="http://play.golang.org/p/smWim1q9ofu"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
+            <a href="http://play.golang.org/p/LnBMavPrkuf"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
           <pre class="chroma"><span class="kn">package</span> <span class="nx">main</span>
 </pre>
           </td>
@@ -83,10 +83,65 @@ base case of <code>fact(0)</code>.</p>
           <td class="docs">
             
           </td>
-          <td class="code">
+          <td class="code leading">
             
           <pre class="chroma"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
     <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nf">fact</span><span class="p">(</span><span class="mi">7</span><span class="p">))</span>
+</pre>
+          </td>
+        </tr>
+        
+        <tr>
+          <td class="docs">
+            <p>Closures can also be recursive, but this requires the
+closure to be declared with a typed <code>var</code> explicitly
+before it&rsquo;s defined.</p>
+
+          </td>
+          <td class="code leading">
+            
+          <pre class="chroma">
+    <span class="kd">var</span> <span class="nx">fib</span> <span class="kd">func</span><span class="p">(</span><span class="nx">n</span> <span class="kt">int</span><span class="p">)</span> <span class="kt">int</span>
+</pre>
+          </td>
+        </tr>
+        
+        <tr>
+          <td class="docs">
+            
+          </td>
+          <td class="code leading">
+            
+          <pre class="chroma">    <span class="nx">fib</span> <span class="p">=</span> <span class="kd">func</span><span class="p">(</span><span class="nx">n</span> <span class="kt">int</span><span class="p">)</span> <span class="kt">int</span> <span class="p">{</span>
+        <span class="k">if</span> <span class="nx">n</span> <span class="p">&lt;</span> <span class="mi">2</span> <span class="p">{</span>
+            <span class="k">return</span> <span class="nx">n</span>
+        <span class="p">}</span>
+        <span class="k">return</span> <span class="nf">fib</span><span class="p">(</span><span class="nx">n</span><span class="o">-</span><span class="mi">1</span><span class="p">)</span> <span class="o">+</span> <span class="nf">fib</span><span class="p">(</span><span class="nx">n</span><span class="o">-</span><span class="mi">2</span><span class="p">)</span>
+</pre>
+          </td>
+        </tr>
+        
+        <tr>
+          <td class="docs">
+            <p>Since <code>fib</code> was previously declared in <code>main</code>, Go
+knows which function to call with <code>fib</code> here.</p>
+
+          </td>
+          <td class="code leading">
+            
+          <pre class="chroma">
+    <span class="p">}</span>
+</pre>
+          </td>
+        </tr>
+        
+        <tr>
+          <td class="docs">
+            
+          </td>
+          <td class="code">
+            
+          <pre class="chroma">    <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nf">fib</span><span class="p">(</span><span class="mi">7</span><span class="p">))</span>
 <span class="p">}</span>
 </pre>
           </td>
@@ -103,7 +158,8 @@ base case of <code>fact(0)</code>.</p>
           <td class="code">
             
           <pre class="chroma"><span class="gp">$</span> go run recursion.go 
-<span class="go">5040</span></pre>
+<span class="go">5040
+</span><span class="go">13</span></pre>
           </td>
         </tr>
         
@@ -120,7 +176,7 @@ base case of <code>fact(0)</code>.</p>
     </div>
     <script>
       var codeLines = [];
-      codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import \"fmt\"\u000A');codeLines.push('func fact(n int) int {\u000A    if n \u003D\u003D 0 {\u000A        return 1\u000A    }\u000A    return n * fact(n-1)\u000A}\u000A');codeLines.push('func main() {\u000A    fmt.Println(fact(7))\u000A}\u000A');codeLines.push('');
+      codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import \"fmt\"\u000A');codeLines.push('func fact(n int) int {\u000A    if n \u003D\u003D 0 {\u000A        return 1\u000A    }\u000A    return n * fact(n-1)\u000A}\u000A');codeLines.push('func main() {\u000A    fmt.Println(fact(7))\u000A');codeLines.push('    var fib func(n int) int\u000A');codeLines.push('    fib \u003D func(n int) int {\u000A        if n \u003C 2 {\u000A            return n\u000A        }\u000A        return fib(n-1) + fib(n-2)\u000A');codeLines.push('    }\u000A');codeLines.push('    fmt.Println(fib(7))\u000A}\u000A');codeLines.push('');
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