c
/
gravity-lang
mirror of https://github.com/marcobambini/gravity.git


			
				
					
						
						
							123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199
							<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>Gravity: Loop</title>
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/normalize/5.0.0/normalize.min.css" />
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
    <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Open+Sans:400,700,800">
    <link rel="stylesheet" href="scripts/highlight/styles/github-gist.css">
    <link rel="stylesheet" href="stylesheets/styles.css">
  </head>
  <body>

	<!-- BEGIN NAVIGATION BAR -->
	<nav class="navbar navbar-default navbar-fixed-top">
		<div class="container">
		<div class="navbar-header">
			<button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbar" aria-expanded="false" aria-controls="navbar">
				<span class="sr-only">Toggle navigation</span>
				<span class="icon-bar"></span>
				<span class="icon-bar"></span>
				<span class="icon-bar"></span>
			</button>
			<a class="navbar-brand" href="http://gravity-lang.org"><img src="images/logo.png" width="32px" height="36px"></a>
		</div>
		<div id="navbar" class="navbar-collapse collapse">
			<ul class="nav navbar-nav navbar-right">
				<li class="active"><a href="index.html">Gravity</a></li>
				<li><a href="internals/index.html">Internals</a></li>
				<li><a href="https://github.com/marcobambini/gravity">GitHub</a></li>
			</ul>
		</div><!--/.nav-collapse -->
	</div>
	</nav>
	<!-- END NAVIGATION BAR -->

	<div class="container body-container">
		<div class="main-content">
			<div class="row">
       	
       		<!-- BEGIN SIDEBAR -->
       		<div class="col-sm-3 border-right section-left">
				<div saveheight="1" class="sidebar-nav">
				<h4>INTRODUCTION</h4>
				<ul>
					<li><a href="index.html"><span>Introduction</span></a></li>
					<li><a href="getting-started.html"><span>Getting Started</span></a></li>
				</ul>
				<h4>LANGUAGE GUIDE</h4>
				<ul>
					<li><a href="syntax.html"><span>Syntax</span></a></li>
					<li><a href="operators.html"><span>Operators</span></a></li>
					<li><a href="types.html"><span>Types</span></a></li>
					<li><a href="lists.html"><span>Lists</span></a></li>
					<li><a href="maps.html"><span>Maps</span></a></li>
					<li><a href="enum.html"><span>Enum</span></a></li>
					<li><a href="functions.html"><span>Functions</span></a></li>
					<li><a href="closures.html"><span>Closures</span></a></li>
					<li><a href="classes.html"><span>Classes</span></a></li>
					<li><a href="control-flow.html"><span>Control Flow</span></a></li>
					<li><a href="loops.html" class="active"><span>Loops</span></a></li>
					<li><a href="fibers.html"><span>Fibers</span></a></li>
				</ul>
				<h4>ADVANCED</h4>
				<ul>
					<li><a href="api.html"><span>Embedding API</span></a></li>
					<li><a href="system.html"><span>System class</span></a></li>
					<li><a href="unit-test.html"><span>Unit test</span></a></li>
					<li><a href="contributing.html"><span>Contributing</span></a></li>
				</ul>
				</div>
			</div>
			<!-- END SIDEBAR -->

       		<div class="col-sm-9 border-left section-right">
         	<h1 class="section-header">Loop</h1><hr>
			
			<p class="section-content">
			
			<h4 class="section-h4">While loop</h4>
			<p>A while loop performs a set of statements until a condition becomes false. These kinds of loops are best used when the number of iterations is not known before the first iteration begins.</p>
			<pre><code class="swift">
	func main() {
		var i = 0;
			
		while (i < 50000) {
			i += 1;
		}
			
		return i;
	}
			</code></pre>
			
			<h4 class="section-h4">Repeat-while loop</h4>
			<p>The other variation of the while loop, known as the repeat-while loop, performs a single pass through the loop block first, before considering the loop’s condition. It then continues to repeat the loop until the condition is false.
			</p>
			<pre><code class="swift">
	func main() {
		var i = 0;
				
		repeat {
			i += 1;
		} while (i < 50000);
				
		return i;
	}
			</code></pre>
			
			<h4 class="section-h4">For loop</h4>
			<p>You can access an element from a list by calling the subscript operator [] on it with the index of the element you want. Like most languages, indices start at zero:</p>
			<pre><code class="swift">
	var count = 0;
	for (var i in 0...40) {
		count += i;
	}
	return count;
			</code></pre>
			<p>The for in loop can be used over any object that supports iteration, such as <a href="lists.html">Lists</a> or <a href="maps.html">Maps</a>.</p>
         	
         	<h4 class="section-h4">Loop method</h4>
         	<p>Performing a loop is very common operation in any programming language, so Gravity adds a very convenient way to run a loop by adding a special loop method to some classes (Int, Range, List and Map) that accepts a <a href="closures.html">closure</a> as parameter:</p>
         	<pre><code class="swift">
	func main() {
		4.loop({System.print("Hello World");});
	}
	// Output:
	// Hello World
	// Hello World
	// Hello World
	// Hello World
         	</code></pre>
         	<p>If we need to access the current index of the loop we can just rewrite the closure:</p>
         	<pre><code class="swift">
	func main() {
		var target = 5;
		target.loop(func (value){System.print("Hello World " + value);});
	}
	// Output:
	// Hello World 0
	// Hello World 1
	// Hello World 2
	// Hello World 3
	// Hello World 4
			</code></pre>
			<p>Loop within a <a href="types.html">Range</a>:</p>
         	<pre><code class="swift">
	func main() {
		var target = 0...4;
		target.loop(func (value){System.print("Hello World " + value);});
	}
	// also in reverse order
	func main() {
		var target = 4...0;
		target.loop(func (value){System.print("Hello World " + value);});
	}
			</code></pre>
			<p>Loop within a <a href="lists.html">List</a>:</p>
         	<pre><code class="swift">
	func main() {
		var target = [10,20,30,40,50,60,70,80,90];
		target.loop(func (value){System.print("Hello World " + value);});
	}
			</code></pre>
			<p>Loop within a <a href="maps.html">Map</a> where key is passed as closure argument (please note that key order is not preserved):</p>
         	<pre><code class="swift">
	func main() {
		var target = ["key1":10,"key2":20,"key3":30,"key4":40];
		target.loop(func (key){System.print(key);});
	}
	// Output:
	// key1
	// key2
	// key4
	// key3
			</code></pre>
         	</div>
       	</div> <!-- /row -->
       </div> <!-- /main-content -->
     </div> <!-- /container -->

	<!-- BEGIN FOOTER -->
	<footer class="navbar-fixed-bottom">
		<div class="container footer">
			<p>
			</p>
		</div>
	</footer>
    <!-- END FOOTER -->
	
	<!-- Bootstrap JS -->
	<script src="https://code.jquery.com/jquery-1.12.4.min.js"></script>
	<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
	
	<!-- Highlights JS -->
    <script src="scripts/highlight/highlight.min.js"></script>
    <script>hljs.initHighlightingOnLoad();</script>
    
	</body>
</html>