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301 lines
11 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>Values – Wren</title>
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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 class="big">
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<a href="./"><img src="./wren.svg" class="logo"></a>
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<ul>
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<li><a href="getting-started.html">Getting Started</a></li>
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<li><a href="contributing.html">Contributing</a></li>
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<li><a href="blog">Blog</a></li>
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<li><a href="try">Try it!</a></li>
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</ul>
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<section>
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<h2>guides</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="values.html">Values</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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<li><a href="method-calls.html">Method Calls</a></li>
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<li><a href="control-flow.html">Control Flow</a></li>
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<li><a href="variables.html">Variables</a></li>
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<li><a href="functions.html">Functions</a></li>
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<li><a href="classes.html">Classes</a></li>
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<li><a href="concurrency.html">Concurrency</a></li>
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<li><a href="error-handling.html">Error Handling</a></li>
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<li><a href="modularity.html">Modularity</a></li>
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</ul>
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</section>
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<section>
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<h2>API docs</h2>
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<ul>
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<li><a href="modules">Modules</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="cli">Wren CLI</a></li>
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<li><a href="embedding">Embedding</a></li>
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<li><a href="performance.html">Performance</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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<nav class="small">
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<table>
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<tr>
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<div><a href="getting-started.html">Getting Started</a></div>
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<div><a href="contributing.html">Contributing</a></div>
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<div><a href="blog">Blog</a></div>
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<div><a href="try">Try it!</a></div>
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</tr>
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<tr>
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<td colspan="2"><h2>guides</h2></td>
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<td><h2>reference</h2></td>
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</tr>
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<tr>
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<td>
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<ul>
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<li><a href="syntax.html">Syntax</a></li>
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<li><a href="values.html">Values</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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<li><a href="method-calls.html">Method Calls</a></li>
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<li><a href="control-flow.html">Control Flow</a></li>
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</ul>
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</td>
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<td>
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<ul>
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<li><a href="variables.html">Variables</a></li>
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<li><a href="functions.html">Functions</a></li>
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<li><a href="classes.html">Classes</a></li>
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<li><a href="concurrency.html">Concurrency</a></li>
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<li><a href="error-handling.html">Error Handling</a></li>
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<li><a href="modularity.html">Modularity</a></li>
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</ul>
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</td>
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<td>
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<ul>
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<li><a href="modules">API/Modules</a></li>
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<li><a href="embedding">Embedding</a></li>
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<li><a href="performance.html">Performance</a></li>
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<li><a href="qa.html">Q & A</a></li>
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</ul>
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</td>
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</tr>
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</table>
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</nav>
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<main>
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<h2>Values</h2>
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<p>Values are the built-in atomic object types that all other objects are composed
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of. They can be created through <em>literals</em>, expressions that evaluate to a
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value. All values are <em>immutable</em>—once created, they do not change. The
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number <code>3</code> is always the number <code>3</code>. The string <code>"frozen"</code> can never have its
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character array modified in place.</p>
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<h2>Booleans <a href="#booleans" name="booleans" class="header-anchor">#</a></h2>
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<p>A boolean value represents truth or falsehood. There are two boolean literals,
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<code>true</code> and <code>false</code>. Their class is <a href="modules/core/bool.html">Bool</a>.</p>
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<h2>Numbers <a href="#numbers" name="numbers" class="header-anchor">#</a></h2>
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<p>Like other scripting languages, Wren has a single numeric type:
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double-precision floating point. Number literals look like you expect coming
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from other languages:</p>
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<pre class="snippet">
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0
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1234
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-5678
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3.14159
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1.0
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-12.34
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0.0314159e02
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0.0314159e+02
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314.159e-02
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0xcaffe2
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</pre>
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<p>Numbers are instances of the <a href="modules/core/num.html">Num</a> class.</p>
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<h2>Strings <a href="#strings" name="strings" class="header-anchor">#</a></h2>
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<p>A string is an array of bytes. Typically, they store characters encoded in
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UTF-8, but you can put any byte values in there, even zero or invalid UTF-8
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sequences. (You might have some trouble <em>printing</em> the latter to your terminal,
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though.)</p>
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<p>String literals are surrounded in double quotes:</p>
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<pre class="snippet">
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"hi there"
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</pre>
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<p>They can also span multiple lines:</p>
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<pre class="snippet">
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"hi
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there,
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again"
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</pre>
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<h3>Escaping <a href="#escaping" name="escaping" class="header-anchor">#</a></h3>
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<p>A handful of escape characters are supported:</p>
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<pre class="snippet">
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"\0" // The NUL byte: 0.
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"\"" // A double quote character.
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"\\" // A backslash.
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"\%" // A percent sign.
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"\a" // Alarm beep. (Who uses this?)
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"\b" // Backspace.
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"\f" // Formfeed.
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"\n" // Newline.
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"\r" // Carriage return.
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"\t" // Tab.
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"\v" // Vertical tab.
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</pre>
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<p>A <code>\u</code> followed by four hex digits can be used to specify a Unicode code point:</p>
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<pre class="snippet">
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System.print("\u0041\u0b83\u00DE") //> AஃÞ
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</pre>
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<p>A capital <code>\U</code> followed by <em>eight</em> hex digits allows Unicode code points outside
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of the basic multilingual plane, like all-important emoji:</p>
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<pre class="snippet">
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System.print("\U0001F64A\U0001F680") //> 🙊🚀
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</pre>
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<p>A <code>\x</code> followed by two hex digits specifies a single unencoded byte:</p>
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<pre class="snippet">
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System.print("\x48\x69\x2e") //> Hi.
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</pre>
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<p>Strings are instances of class <a href="modules/core/string.html">String</a>.</p>
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<h3>Interpolation <a href="#interpolation" name="interpolation" class="header-anchor">#</a></h3>
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<p>String literals also allow <em>interpolation</em>. If you have a percent sign (<code>%</code>)
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followed by a parenthesized expression, the expression is evaluated. The
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resulting object’s <code>toString</code> method is called and the result is inserted in the
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string:</p>
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<pre class="snippet">
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System.print("Math %(3 + 4 * 5) is fun!") //> Math 23 is fun!
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</pre>
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<p>Arbitrarily complex expressions are allowed inside the parentheses:</p>
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<pre class="snippet">
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System.print("wow %((1..3).map {|n| n * n}.join())") //> wow 149
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</pre>
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<p>An interpolated expression can even contain a string literal which in turn has
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its own nested interpolations, but doing that gets unreadable pretty quickly.</p>
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<h3>Raw strings <a href="#raw-strings" name="raw-strings" class="header-anchor">#</a></h3>
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<p>A string literal can also be created using triple quotes <code>"""</code> which is
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parsed as a raw string. A raw string is no different
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from any other string, it’s just parsed in a different way.</p>
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<p><strong>Raw strings do not process escapes and do not apply any interpolation</strong>.</p>
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<pre class="snippet">
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"""hi there"""
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</pre>
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<p>When a raw string spans multiple lines, the newline immediately
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after the triple quote will be ignored, and any whitespace after
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the last newline (before the closing triple quote) will be ignored too.</p>
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<pre class="snippet">
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"""
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Hello world
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"""
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</pre>
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<p>The value in the string above is <code>Hello world</code>, it contains no newlines.
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The newline after <code>"""</code> and the whitespace on the closing line are ignored.
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Note that the whitespace on the line is preserved.</p>
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<p>A raw string will be parsed exactly as is in the file, unmodified.
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This means it can contain quotes, invalid syntax, other data formats
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and so on without being modified by Wren.</p>
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<pre class="snippet">
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"""
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{
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"hello": "wren",
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"from" : "json"
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}
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"""
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</pre>
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<p>One more example, embedding wren code inside a string safely.</p>
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<pre class="snippet">
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"""
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A markdown string with embedded wren code example.
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class Example {
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construct code() {
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//
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}
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}
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"""
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</pre>
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<h2>Ranges <a href="#ranges" name="ranges" class="header-anchor">#</a></h2>
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<p>A range is a little object that represents a consecutive range of numbers. They
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don’t have their own dedicated literal syntax. Instead, the number class
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implements the <code>..</code> and <code>...</code> <a href="method-calls.html#operators">operators</a> to create them:</p>
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<pre class="snippet">
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3..8
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</pre>
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<p>This creates a range from three to eight, including eight itself. If you want a
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half-inclusive range, use <code>...</code>:</p>
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<pre class="snippet">
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4...6
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</pre>
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<p>This creates a range from four to six <em>not</em> including six itself. Ranges are
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commonly used for <a href="control-flow.html#for-statements">iterating</a> over a
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sequences of numbers, but are useful in other places too. You can pass them to
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a <a href="lists.html">list</a>‘s subscript operator to return a subset of the list, for
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example:</p>
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<pre class="snippet">
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var list = ["a", "b", "c", "d", "e"]
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var slice = list[1..3]
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System.print(slice) //> [b, c, d]
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</pre>
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<p>Their class is <a href="modules/core/range.html">Range</a>.</p>
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<h2>Null <a href="#null" name="null" class="header-anchor">#</a></h2>
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<p>Wren has a special value <code>null</code>, which is the only instance of the class
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<a href="modules/core/null.html">Null</a>. (Note the difference in case.) It functions a bit like <code>void</code> in some
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languages: it indicates the absence of a value. If you call a method that
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doesn’t return anything and get its returned value, you get <code>null</code> back.</p>
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<p><br><hr>
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<a class="right" href="lists.html">Lists →</a>
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<a href="syntax.html">← Syntax</a></p>
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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
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<a href="https://github.com/wren-lang/wren">on GitHub</a>
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— Made with ❤ by
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<a href="http://journal.stuffwithstuff.com/">Bob Nystrom</a> and
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<a href="https://github.com/wren-lang/wren/blob/main/AUTHORS">friends</a>.
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</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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