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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>Hyperlinked ECMA C# Language Specification</title><meta name="author" content="Jon Jagger" /><link rel="stylesheet" href="ecma334.css"></link></head><body><div align="right"><em><a href="http://www.jaggersoft.com">Jon Jagger</a></em></div><div align="right"><a href="mailto:jon@jaggersoft.com">jon@jaggersoft.com</a></div><form method="get" action="http://search.atomz.com/search/"><input size="30" name="sp-q"></input><input type="submit" value="Search C# Spec"></input><input type="hidden" name="sp-a" value="sp10024177"></input><input type="hidden" name="sp-f" value="ISO-8859-1"></input></form><a href="toc.htm">Table of Contents</a> <a href="1.htm">1</a> <a href="2.htm">2</a> <a href="3.htm">3</a> <a href="4.htm">4</a> <a href="5.htm">5</a> <a href="6.htm">6</a> <a href="7.htm">7</a> <a href="8.htm">8</a> <a href="9.htm">9</a> <a href="10.htm">10</a> <a href="11.htm">11</a> <a href="12.htm">12</a> <a href="13.htm">13</a> <a href="14.htm">14</a> <a href="15.htm">15</a> <a href="16.htm">16</a> <a href="17.htm">17</a> <a href="18.htm">18</a> <a href="19.htm">19</a> <a href="20.htm">20</a> <a href="21.htm">21</a> <a href="22.htm">22</a> <a href="23.htm">23</a> <a href="24.htm">24</a> <a href="25.htm">25</a> <a href="notes.htm">Notes</a> <a href="HyperlinkedCSharpECMA.zip">Download</a><span class="ruler"></span><span class="heading">ECMA-334 C# Language Specification</span><span class="navigate"><a href="8.2.2.htm"><img src="previous.gif" alt="previous" border="0" /></a><a href="8.2.4.htm"><img src="next.gif" alt="next" border="0" /></a></span><span class="clause-depth"><a href="7.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="9.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number-link"><a href="8.htm">8</a></span><span class="clause-title-previous"> Language Overview</span></span><span class="clause-depth"><a href="8.1.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="8.3.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number-link"><a href="8.2.htm">8.2</a></span><span class="clause-title-previous"> Types</span></span><span class="clause-depth"><a href="8.2.2.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="8.2.4.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number">8.2.3</span><span class="clause-title"> Array types</span></span><span class="informative"><span class="paragraph">Arrays may be single-dimensional or multi-dimensional. Both "rectangular" and "jagged" arrays are supported. </span><span class="paragraph">Single-dimensional arrays are the most common type. The example <pre class="code-example">
using System;  
class Test  
{  
   static void Main() {  
      int[] arr = new int[5];  
      for (int i = 0; i &lt; arr.Length; i++)  
      arr[i] = i * i;  
      for (int i = 0; i &lt; arr.Length; i++)  
      Console.WriteLine("arr[{0}] = {1}", i, arr[i]);  
   }  
}  
</pre>creates a single-dimensional array of <span class="keyword">int</span> values, initializes the array elements, and then prints each of them out. The output produced is: <pre class="code-example">
arr[0] = 0  
arr[1] = 1  
arr[2] = 4  
arr[3] = 9  
arr[4] = 16  
</pre></span><span class="paragraph">The type int[] used in the previous example is an array type. Array types are written using a  <span class="non-terminal"><a href="19.1.htm#non-array-type">non-array-type</a></span> followed by one or more rank specifiers. The example <pre class="code-example">
class Test  
{  
   static void Main() {  
      int[] a1;    // single-dimensional array of int  
      int[,] a2;    // 2-dimensional array of int  
      int[,,] a3;   // 3-dimensional array of int  
      int[][] j2;     // "jagged" array: array of (array of int)  
      int[][][] j3;    // array of (array of (array of int))  
   }  
}  
</pre>shows a variety of local variable declarations that use array types with <span class="keyword">int</span> as the element type. </span><span class="paragraph">Array types are reference types, and so the declaration of an array variable merely sets aside space for the reference to the array. Array instances are actually created via array initializers and array creation expressions. The example <pre class="code-example">
class Test  
{  
   static void Main() {  
      int[] a1 = new int[] {1, 2, 3};  
      int[,] a2 = new int[,] {{1, 2, 3}, {4, 5, 6}};  
      int[,,] a3 = new int[10, 20, 30];  
      int[][] j2 = new int[3][];  
      j2[0] = new int[] {1, 2, 3};  
      j2[1] = new int[] {1, 2, 3, 4, 5, 6};  
      j2[2] = new int[] {1, 2, 3, 4, 5, 6, 7, 8, 9};  
   }  
}  
</pre>shows a variety of array creation expressions. The variables a1, a2 and a3 denote rectangular arrays, and the variable j2 denotes a jagged array. It should be no surprise that these terms are based on the shapes of the arrays. Rectangular arrays always have a rectangular shape. Given the length of each dimension of the array, its rectangular shape is clear. For example, the lengths of a3's three dimensions are 10, 20, and 30, respectively, and it is easy to see that this array contains 10*20*30 elements. </span><span class="paragraph">In contrast, the variable j2 denotes a "jagged" array, or an "array of arrays". Specifically, j2 denotes an array of an array of <span class="keyword">int</span>, or a single-dimensional array of type int[]. Each of these int[] variables can be initialized individually, and this allows the array to take on a jagged shape. The example gives each of the int[] arrays a different length. Specifically, the length of j2[0] is 3, the length of j2[1] is 6, and the length of j2[2] is 9. </span><span class="paragraph"><span class="note">[Note: In C++, an array declared as <span class="keyword">int</span> x[3][5][7] would be considered a three dimensional rectangular array, while in C#, the declaration int[][][] declares a jagged array type. end note]</span> </span><span class="paragraph">The element type and shape of an array-including whether it is jagged or rectangular, and the number of dimensions it has-are part of its type. On the other hand, the size of the array-as represented by the length of each of its dimensions-is not part of an array's type. This split is made clear in the language syntax, as the length of each dimension is specified in the array creation expression rather than in the array type. For instance the declaration <pre class="code-example">
int[,,] a3 = new int[10, 20, 30];  
</pre>has an array type of int[,,] and an array creation expression of new int[10, 20, 30]. </span><span class="paragraph">For local variable and field declarations, a shorthand form is permitted so that it is not necessary to re-state the array type. For instance, the example <pre class="code-example">
int[] a1 = new int[] {1, 2, 3};  
</pre>can be shortened to <pre class="code-example">
int[] a1 = {1, 2, 3};  
</pre>without any change in program semantics. </span><span class="paragraph">The context in which an array initializer such as {1, 2, 3} is used determines the type of the array being initialized. The example <pre class="code-example">
class Test  
{  
   static void Main() {  
      short[] a = {1, 2, 3};  
      int[] b = {1, 2, 3};  
      long[] c = {1, 2, 3};  
   }  
}  
</pre>shows that the same array initializer syntax can be used for several different array types. Because context is required to determine the type of an array initializer, it is not possible to use an array initializer in an expression context without explicitly stating the type of the array. </span></span><span class="ruler"></span><table><tr><td><table align="left" bgcolor="navy"><tr bgcolor="navy"><td><font face="Arial,sans-serif" size="6" color="yellow"><strong>{ JSL }</strong></font></td></tr></table></td></tr><tr><td><font face="Arial,sans-serif" size="2" color="navy"><strong>Jagger Software Ltd</strong></font></td></tr><tr><td><font face="Arial,sans-serif" size="2" color="navy"><strong>Company # 4070126</strong></font></td></tr><tr><td><font face="Arial,sans-serif" size="2" color="navy"><strong>VAT # 762 5213 42</strong></font></td></tr></table><img src="valid-html401.png" align="left" height="31" width="88" alt="Valid HTML 4.01" /><img src="vcss.gif" align="left" height="31" width="88" alt="Valid CSS" /></body></html>
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