38 lines
1.3 KiB
XML
38 lines
1.3 KiB
XML
<?xml version="1.0"?>
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<clause number="8.7.8" title="Instance constructors" informative="true">
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<paragraph>An instance constructor is a member that implements the actions required to initialize an instance of a class. </paragraph>
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<paragraph>The example <code_example><![CDATA[
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using System;
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class Point
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{
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public double x, y;
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public Point() {
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this.x = 0;
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this.y = 0;
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}
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public Point(double x, double y) {
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this.x = x;
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this.y = y;
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}
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public static double Distance(Point a, Point b) {
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double xdiff = a.x - b.x;
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double ydiff = a.y - b.y;
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return Math.Sqrt(xdiff * xdiff + ydiff * ydiff);
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}
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public override string ToString() {
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return string.Format("({0}, {1})", x, y);
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}
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}
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class Test
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{
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static void Main() {
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Point a = new Point();
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Point b = new Point(3, 4);
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double d = Point.Distance(a, b);
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Console.WriteLine("Distance from {0} to {1} is {2}", a, b, d);
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}
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}
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]]></code_example>shows a Point class that provides two public instance constructors, one of which takes no arguments, while the other takes two <keyword>double</keyword> arguments. </paragraph>
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<paragraph>If no instance constructor is supplied for a class, then an empty one with no parameters is automatically provided. </paragraph>
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</clause>
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