documenting the and combinator

Author: disnet

doc/main/contracts.html

@@ -137,6 +137,7 @@ <h1 class="title">Contracts.js Documentation</h1>
 </ul></li>
 <li><a href="#combinators"><span class="toc-section-number">4.5</span> Combinators</a><ul>
 <li><a href="#or"><span class="toc-section-number">4.5.1</span> <code>or</code></a></li>
+<li><a href="#and"><span class="toc-section-number">4.5.2</span> <code>and</code></a></li>
 </ul></li>
 <li><a href="#naming-contracts"><span class="toc-section-number">4.6</span> Naming Contracts</a></li>
 <li><a href="#recursive-contracts"><span class="toc-section-number">4.7</span> Recursive Contracts</a></li>
@@ -410,14 +411,22 @@ <h3 id="proxied-arrays"><span class="header-section-number">4.4.2</span> Proxied
 arr[0] = &quot;string&quot;;          // error wrong type</code></pre>
 <h2 id="combinators"><span class="header-section-number">4.5</span> Combinators</h2>
 <h3 id="or"><span class="header-section-number">4.5.1</span> <code>or</code></h3>
-<p>You can combine two contracts with the <code>or</code> combinator. If the first contract fails, the combined contract will succeed if the second passes.</p>
+<p>You can combine two or more contracts with the <code>or</code> combinator. If the first contract fails, the combined contract will succeed if the second passes.</p>
 <pre class="js"><code>@ (Num or Str) -&gt; Str
 function foo(x) { return x.toString(); }
 
 foo(24);    // passes
 foo(&quot;24&quot;);  // passes
 foo(false); // error not a Num or Str</code></pre>
 <p>Note that <code>or</code> only makes sense for at most one higher-order contract. For example, <code>Num or (Num) -&gt; Num</code> is fine but <code>(Num) -&gt; Num or (Str) -&gt; Str</code> will not work.</p>
+<h3 id="and"><span class="header-section-number">4.5.2</span> <code>and</code></h3>
+<p>You can combine two or more contracts with the <code>and</code> combinator. Both contracts must pass for the combined contract to succeed.</p>
+<pre class="js"><code>@ (Num and (x) =&gt; x &gt; 5) -&gt; Num
+function foo(x) { return x; }
+
+foo(10);   // passes
+foo(&quot;10&quot;); // fails
+foo(1);    // fails</code></pre>
 <h2 id="naming-contracts"><span class="header-section-number">4.6</span> Naming Contracts</h2>
 <p>When you have a complicated contract that is repeated in several places it can be convenient to refer to it by a shorter name. For this, you can use <code>let</code> after the <code>@</code> symbol:</p>
 <pre class="js"><code>@ let NumId = (Num) -&gt; Num

doc/main/contracts.md

@@ -384,8 +384,8 @@ arr[0] = "string";          // error wrong type
 
 ### `or`
 
-You can combine two contracts with the `or` combinator. If the first
-contract fails, the combined contract will succeed if the second
+You can combine two or more contracts with the `or` combinator. If the
+first contract fails, the combined contract will succeed if the second
 passes.
 
 ```js
@@ -401,6 +401,20 @@ Note that `or` only makes sense for at most one higher-order contract.
 For example, `Num or (Num) -> Num` is fine but `(Num) -> Num or
 (Str) -> Str` will not work.
 
+### `and`
+
+You can combine two or more contracts with the `and` combinator.
+Both contracts must pass for the combined contract to succeed.
+
+```js
+@ (Num and (x) => x > 5) -> Num
+function foo(x) { return x; }
+
+foo(10);   // passes
+foo("10"); // fails
+foo(1);    // fails
+```
+
 
 ## Naming Contracts