11.1.1.htm
来自「This ECMA Standard specifies the form an」· HTM 代码 · 共 13 行
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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="11.1.htm"><img src="previous.gif" alt="previous" border="0" /></a><a href="11.1.2.htm"><img src="next.gif" alt="next" border="0" /></a></span><span class="clause-depth"><a href="10.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="12.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number-link"><a href="11.htm">11</a></span><span class="clause-title-previous"> Types</span></span><span class="clause-depth"><a href="11.1.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="11.2.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number-link"><a href="11.1.htm">11.1</a></span><span class="clause-title-previous"> Value types</span></span><span class="clause-depth"><a href="11.1.1.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="11.1.2.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number">11.1.1</span><span class="clause-title"> Default constructors</span></span><span class="locator">
Paragraph 1</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P1S1"></a>All value types implicitly declare a public parameterless instance constructor called the default constructor.</span> </span><span class="locator">
Paragraph 2</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P2S1"></a>The default constructor returns a zero-initialized instance known as the default value for the value type: </span><ul><li><span class="sentence"><span class="sentence-number">2</span> <a name="P2S2"></a> For all <span class="non-terminal"><a href="11.1.htm#simple-type">simple-type</a></span>s, the default value is the value produced by a bit pattern of all zeros: </span></li><ul><li><span class="sentence"><span class="sentence-number">3</span> <a name="P2S3"></a> For <span class="keyword">sbyte</span>, <span class="keyword">byte</span>, <span class="keyword">short</span>, <span class="keyword">ushort</span>, <span class="keyword">int</span>, <span class="keyword">uint</span>, <span class="keyword">long</span>, and <span class="keyword">ulong</span>, the default value is 0.</span> </li><li><span class="sentence"><span class="sentence-number">4</span> <a name="P2S4"></a> For <span class="keyword">char</span>, the default value is '\x0000'.</span> </li><li><span class="sentence"><span class="sentence-number">5</span> <a name="P2S5"></a> For <span class="keyword">float</span>, the default value is 0.0f.</span> </li><li><span class="sentence"><span class="sentence-number">6</span> <a name="P2S6"></a> For <span class="keyword">double</span>, the default value is 0.0d.</span> </li><li><span class="sentence"><span class="sentence-number">7</span> <a name="P2S7"></a> For <span class="keyword">decimal</span>, the default value is 0.0m.</span> </li><li><span class="sentence"><span class="sentence-number">8</span> <a name="P2S8"></a> For <span class="keyword">bool</span>, the default value is false.</span> </li></ul><li><span class="sentence"><span class="sentence-number">9</span> <a name="P2S9"></a> For an <span class="non-terminal"><a href="11.1.htm#enum-type">enum-type</a></span> E, the default value is 0.</span> </li><li><span class="sentence"><span class="sentence-number">10</span> <a name="P2S10"></a> For a <span class="non-terminal"><a href="11.1.htm#struct-type">struct-type</a></span>, the default value is the value produced by setting all value type fields to their default value and all reference type fields to null.</span> </li></ul></span><span class="locator">
Paragraph 3</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P3S1"></a>Like any other instance constructor, the default constructor of a value type is invoked using the new operator.</span> <span class="note">[Note: For efficiency reasons, this requirement is not intended to actually have the implementation generate a constructor call. end note]</span> <span class="sentence"><span class="sentence-number">2</span> <a name="P3S2"></a>In the example below, variables i and j are both initialized to zero.</span> <pre class="code-example">
class A
{
void F() {
int i = 0;
int j = new int();
}
}
</pre></span><span class="locator">
Paragraph 4</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P4S1"></a>Because every value type implicitly has a public parameterless instance constructor, it is not possible for a struct type to contain an explicit declaration of a parameterless constructor.</span> <span class="sentence"><span class="sentence-number">2</span> <a name="P4S2"></a>A struct type is however permitted to declare parameterized instance constructors (<a href="18.3.8.htm">§18.3.8</a>).</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>⌨️ 快捷键说明
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