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172 lines
8.8 KiB
HTML
<!DOCTYPE html>
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<html>
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<head>
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<meta http-equiv="Content-type" content="text/html;charset=UTF-8" />
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<title>Syntax – Wren</title>
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<link rel="stylesheet" type="text/css" href="style.css" />
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<link href='//fonts.googleapis.com/css?family=Source+Sans+Pro:400,700,400italic,700italic|Source+Code+Pro:400|Lato:400|Sanchez:400italic,400' rel='stylesheet' type='text/css'>
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the viewport. -->
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<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1"/>
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</head>
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<body id="top">
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<header>
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<div class="page">
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<div class="main-column">
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<h1><a href="./">wren</a></h1>
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<h2>a classy little scripting language</h2>
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</div>
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</div>
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</header>
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<div class="page">
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<nav>
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<ul>
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<li><a href="getting-started.html">Getting Started</a></li>
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</ul>
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<section>
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<h2>language</h2>
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<ul>
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<li><a href="syntax.html">Syntax</a></li>
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<li><a href="expressions.html">Expressions</a></li>
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<li><a href="variables.html">Variables</a></li>
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<li><a href="control-flow.html">Control Flow</a></li>
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<li><a href="error-handling.html">Error Handling</a></li>
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<li><a href="modules.html">Modules</a></li>
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</ul>
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</section>
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<section>
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<h2>types</h2>
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<ul>
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<li><a href="values.html">Values</a></li>
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<li><a href="classes.html">Classes</a></li>
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<li><a href="fibers.html">Fibers</a></li>
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<li><a href="functions.html">Functions</a></li>
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<li><a href="lists.html">Lists</a></li>
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<li><a href="maps.html">Maps</a></li>
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</ul>
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</section>
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<section>
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<h2>reference</h2>
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<ul>
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<li><a href="core">Core Library</a></li>
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<li><a href="embedding-api.html">Embedding API</a></li>
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<li><a href="performance.html">Performance</a></li>
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<li><a href="community.html">Community</a></li>
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<li><a href="contributing.html">Contributing</a></li>
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<li><a href="qa.html">Q & A</a></li>
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</ul>
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</section>
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</nav>
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<main>
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<h1>Syntax</h1>
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<p>Wren's syntax is designed to be familiar to people coming from C-like languages
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while being a bit simpler and more streamlined.</p>
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<p>Scripts are stored in plain text files with a <code>.wren</code> file extension. Wren does
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not compile ahead of time: programs are run directly from source, from top to
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bottom like a typical scripting language. (Internally, programs are compiled to
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bytecode for efficiency, but that's an implementation detail.)</p>
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<h2>Comments <a href="#comments" name="comments" class="header-anchor">#</a></h2>
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<p>Line comments start with <code>//</code> and end at the end of the line:</p>
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<div class="codehilite"><pre><span class="c1">// This is a comment.</span>
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</pre></div>
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<p>Block comments start with <code>/*</code> and end with <code>*/</code>. They can span multiple lines
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or be within a single one. Unlike C, block comments can nest in Wren:</p>
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<div class="codehilite"><pre><span class="cm">/* This is /* a nested */ comment. */</span>
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</pre></div>
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<h2>Reserved words <a href="#reserved-words" name="reserved-words" class="header-anchor">#</a></h2>
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<p>Some people like to see all of the reserved words in a programming language in
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one lump. If you're one of those folks, here you go:</p>
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<div class="codehilite"><pre><span class="k">break</span> <span class="k">class</span> <span class="k">construct</span> <span class="k">else</span> <span class="kc">false</span> <span class="k">for</span> <span class="k">foreign</span> <span class="k">if</span> <span class="k">import</span>
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<span class="k">in</span> <span class="k">is</span> <span class="kc">null</span> <span class="k">return</span> <span class="k">static</span> <span class="k">super</span> <span class="nb">this</span> <span class="kc">true</span> <span class="k">var</span> <span class="k">while</span>
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</pre></div>
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<h2>Identifiers <a href="#identifiers" name="identifiers" class="header-anchor">#</a></h2>
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<p>Naming rules are similar to other programming languages. Identifiers start with
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a letter or underscore and may contain letters, digits, and underscores. Case
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is sensitive.</p>
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<div class="codehilite"><pre><span class="n">hi</span>
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<span class="n">camelCase</span>
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<span class="vg">PascalCase</span>
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<span class="vi">_under_score</span>
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<span class="n">abc123</span>
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<span class="vg">ALL_CAPS</span>
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</pre></div>
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<p>Identifiers that start with underscore (<code>_</code>) are special in Wren. They are used
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to indicate <a href="classes.html#fields">fields</a> in classes.</p>
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<h2>Newlines <a href="#newlines" name="newlines" class="header-anchor">#</a></h2>
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<p>Newlines (<code>\n</code>) are meaningful in Wren. They are used to separate statements:</p>
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<div class="codehilite"><pre><span class="c1">// Two statements:</span>
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<span class="vg">System</span><span class="o">.</span><span class="n">print</span><span class="p">(</span><span class="s">"hi"</span><span class="p">)</span> <span class="c1">// Newline.</span>
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<span class="vg">System</span><span class="o">.</span><span class="n">print</span><span class="p">(</span><span class="s">"bye"</span><span class="p">)</span>
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</pre></div>
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<p>Sometimes, though, a statement doesn't fit on a single line and jamming a
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newline in the middle would trip it up. To handle that, Wren has a very simple
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rule: It ignores a newline following any token that can't end a statement.</p>
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<div class="codehilite"><pre><span class="vg">System</span><span class="o">.</span><span class="n">print</span><span class="p">(</span> <span class="c1">// Newline here is ignored.</span>
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<span class="s">"hi"</span><span class="p">)</span>
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</pre></div>
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<p>In practice, this means you can put each statement on its own line and wrap
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them across lines as needed without too much trouble.</p>
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<h2>Blocks <a href="#blocks" name="blocks" class="header-anchor">#</a></h2>
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<p>Wren uses curly braces to define <em>blocks</em>. You can use a block anywhere a
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statement is allowed, like in <a href="control-flow.html">control flow</a> statements.
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<a href="classes.html#methods">Method</a> and <a href="functions.html">function</a> bodies are also
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blocks. For example, here we have a block for the then case, and a single
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statement for the else:</p>
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<div class="codehilite"><pre><span class="k">if</span> <span class="p">(</span><span class="n">happy</span> <span class="o">&&</span> <span class="n">knowIt</span><span class="p">)</span> <span class="p">{</span>
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<span class="n">hands</span><span class="o">.</span><span class="n">clap</span>
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<span class="p">}</span> <span class="k">else</span> <span class="vg">System</span><span class="o">.</span><span class="n">print</span><span class="p">(</span><span class="s">"sad"</span><span class="p">)</span>
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</pre></div>
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<p>Blocks have two similar but not identical forms. Typically, blocks contain a
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series of statements like:</p>
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<div class="codehilite"><pre><span class="p">{</span>
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<span class="vg">System</span><span class="o">.</span><span class="n">print</span><span class="p">(</span><span class="s">"one"</span><span class="p">)</span>
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<span class="vg">System</span><span class="o">.</span><span class="n">print</span><span class="p">(</span><span class="s">"two"</span><span class="p">)</span>
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<span class="vg">System</span><span class="o">.</span><span class="n">print</span><span class="p">(</span><span class="s">"three"</span><span class="p">)</span>
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<span class="p">}</span>
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</pre></div>
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<p>Blocks of this form when used for method and function bodies automatically
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return <code>null</code> after the block has completed. If you want to return a different
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value, you need an explicit <code>return</code> statement.</p>
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<p>However, it's pretty common to have a method or function that just evaluates
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and returns the result of a single expression. For that, Wren has a more
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compact notation:</p>
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<div class="codehilite"><pre><span class="p">{</span> <span class="s">"single expression"</span> <span class="p">}</span>
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</pre></div>
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<p>If there is no newline after the <code>{</code> (or after the parameter list in a
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<a href="functions.html">function</a>), then the block may only contain a single
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expression, and it automatically returns the result of it. It's exactly the
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same as doing:</p>
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<div class="codehilite"><pre><span class="p">{</span>
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<span class="k">return</span> <span class="s">"single expression"</span>
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<span class="p">}</span>
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</pre></div>
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</main>
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</div>
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<footer>
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<div class="page">
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<div class="main-column">
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<p>Wren lives <a href="https://github.com/munificent/wren">on GitHub</a> — Made with ❤ by <a href="http://journal.stuffwithstuff.com/">Bob Nystrom</a> and <a href="https://github.com/munificent/wren/blob/master/AUTHORS">friends</a>.</p>
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<div class="main-column">
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</div>
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</footer>
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</body>
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</html>
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