c
/
gravity-lang
镜像自地址 https://github.com/marcobambini/gravity.git


			
				
					
						
						
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    <title>Gravity: Types</title>
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				<h4>INTRODUCTION</h4>
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					<li><a href="index.html"><span>Introduction</span></a></li>
					<li><a href="getting-started.html"><span>Getting Started</span></a></li>
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				<h4>LANGUAGE GUIDE</h4>
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					<li><a href="syntax.html"><span>Syntax</span></a></li>
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         	<h1 class="section-header">Values and Types</h1><hr>
			
			<p class="section-content">
			Gravity is a dynamically typed language so variables do not have a type, although they refer to a value that does have a type. In Gravity everything is an object (with methods you can call and instance variables you can use). Basic intrinsic types are of class Object, Int, Float, String, Bool, Null, <a href="classes.html">Class</a>, <a href="functions.html">Function</a>, Fiber, Instance, <a href="lists.html">List</a>, <a href="maps.html">Map</a> and Range.
			</p>
			
			<h4 class="section-h4">Object</h4>
			<p>Object is the root class of every object inside Gravity. Through the Object class, objects inherit a basic interface to the runtime system and the ability to behave as Gravity objects.</p>
			
			<h4 class="section-h4">Int</h4>
			<p>An Int represents a 64 bits (can optionally be compiled as 32bit) signed number:</p>
			<pre><code class="swift">
	var a = 123;		// decimal
	var b = 0xFF;		// hexadecimal
	var c = 0O7777;		// octal
	var d = 0B0101;		// binary

	var e = Int.random(1, 10) // Returns a random integer between 1 and 10 inclusive
			</code></pre>
			
			<h4 class="section-h4">Float</h4>
			<p>A float represents a 32 bits (or better) floating point number:</p>
			<pre><code class="swift">
	var a = 3.1415;		// float
	var b = 1.25e2;		// scientific notation
			</code></pre>
			
			<h4 class="section-h4">String</h4>
			<p>Strings are an immutable sequence of characters. String literals can be surrounded in double or single quotes.</p>
			<pre><code class="swift">
	var a = "Hello World";  // double quotes
	var b = 'Hello World';  // single quotes
	
	// Strings have also a length property
	var n = b.length;       // n is now 11

	// Strings also have some built in methods
	n = b.index("Wor")      // n is now 6.

	n = b.count("l")        // n is now 3.
	n = b.count("llo")      // n is now 1.

	n = "A".repeat(10)      // n is now "AAAAAAAAAA"

	// upper() and lower() operate on the whole string when 0 arguments are passed
	n = b.upper()           // n is now "HELLO WORLD"
	n = b.lower()           // n is now "hello world"

	// upper() and lower() can both take multiple integer arguments
	n = b.upper(1, -1)     // n is now "HEllo WorlD"

	// split() is the opposite of a list join
	var string = "Roses are Red, Violets are Blue"
	var list = string.split(", ")
	list[0]                // "Roses are Red"
	list[1]                // "Violets are Blue"

	// You are also able to edit strings by character...
	b[0] = "Z"              // b is now "Zello World"
	b[1] = "abc"            // b is now "Zabco World"
	b[-7] = "QWERTY"        // b is now "ZabcQWERTYd"

	// and retrieve those characters
	n = a[6]                // n is now "W"
	n = a[-7]               // n is now "o"
	n = a[0...4]            // n is now "Hello"
	n = a[-5...-1]          // n is now "World"
	n = a[-5...10]          // n is now "World"
	n = a[-1...-5]          // n is now "dlroW"
			</code></pre>
			
			<h4 class="section-h4">Bool</h4>
			<p>The bool data type can have only two values, they are the literals true and false. A Bool value expresses the validity of a condition (tells whether the condition is true or false).</p>
			<pre><code class="swift">
	var a = true;
	var b = false;
			</code></pre>
			
			<h4 class="section-h4">Null</h4>
			<p>It indicates the absence of a value. If you call a method that doesn’t return anything and get its returned value, you get null back. The null data type is also used to initialize uninitialized variables with a default value.</p>
			<pre><code class="swift">
	class Newton {
		var mass = 10;
		var acceleration;
		func force() {
			return mass * acceleration;
		}
	}
			
	func f2() {
		var sir = Newton();
		// acceleration instance variable has no default value
		// so it is automatically set to null
		return sir.force();
	}
			
	func f1() {
		var a;
		// a is uninitialized so it has a default null value
		return a;
	}
			</code></pre>
			
			<h4 class="section-h4">Range</h4>
			<p>A range is an object that represents a consecutive range of numbers. Syntax for this type has been directly inspired by Swift.</p>
			<pre><code class="swift">
	// a represents a range with values 1,2,3
	var a = 1...3;
	
	// b represents a range with values 1,2
	var b = 1..<3;
	
	// Ranges have also a conveniente count property
	var n1 = a.count;	// n1 is now 3
	var n2 = b.count;	// n2 is now 2
			</code></pre>
			
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