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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="9.4.4.2.htm"><img src="previous.gif" alt="previous" border="0" /></a><a href="9.4.4.4.htm"><img src="next.gif" alt="next" border="0" /></a></span><span class="clause-depth"><a href="8.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="10.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number-link"><a href="9.htm">9</a></span><span class="clause-title-previous"> Lexical structure</span></span><span class="clause-depth"><a href="9.3.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="9.5.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number-link"><a href="9.4.htm">9.4</a></span><span class="clause-title-previous"> Tokens</span></span><span class="clause-depth"><a href="9.4.3.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="9.4.5.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number-link"><a href="9.4.4.htm">9.4.4</a></span><span class="clause-title-previous"> Literals</span></span><span class="clause-depth"><a href="9.4.4.2.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="9.4.4.4.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number">9.4.4.3</span><span class="clause-title"> Real literals</span></span><span class="locator">
Paragraph 1</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P1S1"></a>Real literals are used to write values of types <span class="keyword">float</span>, <span class="keyword">double</span>, and <span class="keyword">decimal</span>.</span> <span class="grammar-production"><span class="name"><a name="real-literal"></a>real-literal</span> :: <span class="rhs"><span class="non-terminal"><a href="9.4.4.2.htm#decimal-digits">decimal-digits</a></span> <span class="terminal">.</span> <span class="non-terminal"><a href="9.4.4.2.htm#decimal-digits">decimal-digits</a></span> <span class="non-terminal"><a href="9.4.4.3.htm#exponent-part">exponent-part</a></span><sub>opt</sub> <span class="non-terminal"><a href="9.4.4.3.htm#real-type-suffix">real-type-suffix</a></span><sub>opt</sub> </span><span class="rhs"><span class="terminal">.</span> <span class="non-terminal"><a href="9.4.4.2.htm#decimal-digits">decimal-digits</a></span> <span class="non-terminal"><a href="9.4.4.3.htm#exponent-part">exponent-part</a></span><sub>opt</sub> <span class="non-terminal"><a href="9.4.4.3.htm#real-type-suffix">real-type-suffix</a></span><sub>opt</sub> </span><span class="rhs"><span class="non-terminal"><a href="9.4.4.2.htm#decimal-digits">decimal-digits</a></span> <span class="non-terminal"><a href="9.4.4.3.htm#exponent-part">exponent-part</a></span> <span class="non-terminal"><a href="9.4.4.3.htm#real-type-suffix">real-type-suffix</a></span><sub>opt</sub> </span><span class="rhs"><span class="non-terminal"><a href="9.4.4.2.htm#decimal-digits">decimal-digits</a></span> <span class="non-terminal"><a href="9.4.4.3.htm#real-type-suffix">real-type-suffix</a></span> </span></span><span class="grammar-production"><span class="name"><a name="exponent-part"></a>exponent-part</span> :: <span class="rhs"><span class="terminal">e</span> <span class="non-terminal"><a href="9.4.4.3.htm#sign">sign</a></span><sub>opt</sub> <span class="non-terminal"><a href="9.4.4.2.htm#decimal-digits">decimal-digits</a></span> </span><span class="rhs"><span class="terminal">E</span> <span class="non-terminal"><a href="9.4.4.3.htm#sign">sign</a></span><sub>opt</sub> <span class="non-terminal"><a href="9.4.4.2.htm#decimal-digits">decimal-digits</a></span> </span></span><span class="grammar-production"><span class="name"><a name="sign"></a>sign</span> :: one of <span class="rhs"><span class="terminal">+</span> <span class="terminal">-</span> </span></span><span class="grammar-production"><span class="name"><a name="real-type-suffix"></a>real-type-suffix</span> :: one of <span class="rhs"><span class="terminal">F f D d M m </span></span></span></span><span class="locator">
Paragraph 2</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P2S1"></a>If no <span class="non-terminal"><a href="9.4.4.3.htm#real-type-suffix">real-type-suffix</a></span> is specified, the type of the real literal is <span class="keyword">double</span>.</span> <span class="sentence"><span class="sentence-number">2</span> <a name="P2S2"></a>Otherwise, the <span class="non-terminal"><a href="9.4.4.3.htm#real-type-suffix">real-type-suffix</a></span> determines the type of the real literal, as follows: </span><ul><li><span class="sentence"><span class="sentence-number">3</span> <a name="P2S3"></a> A real literal suffixed by F or f is of type <span class="keyword">float</span>.</span> <span class="example">[Example: For example, the literals 1f, 1.5f, 1e10f, and 123.456F are all of type <span class="keyword">float</span>. end example]</span> </li><li><span class="sentence"><span class="sentence-number">4</span> <a name="P2S4"></a> A real literal suffixed by D or d is of type <span class="keyword">double</span>.</span> <span class="example">[Example: For example, the literals 1d, 1.5d, 1e10d, and 123.456D are all of type <span class="keyword">double</span>. end example]</span> </li><li><span class="sentence"><span class="sentence-number">5</span> <a name="P2S5"></a> A real literal suffixed by M or m is of type <span class="keyword">decimal</span>.</span> <span class="example">[Example: For example, the literals 1m, 1.5m, 1e10m, and 123.456M are all of type <span class="keyword">decimal</span>. end example]</span> <span class="sentence"><span class="sentence-number">6</span> <a name="P2S6"></a>This literal is converted to a <span class="keyword">decimal</span> value by taking the exact value, and, if necessary, rounding to the nearest representable value using banker's rounding (<a href="11.1.6.htm">§11.1.6</a>).</span> <span class="sentence"><span class="sentence-number">7</span> <a name="P2S7"></a>Any scale apparent in the literal is preserved unless the value is rounded or the value is zero (in which latter case the sign and scale will be 0).</span> <span class="note">[Note: Hence, the literal 2.900m will be parsed to form the <span class="keyword">decimal</span> with sign 0, coefficient 2900, and scale 3. end note]</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>If the specified literal cannot be represented in the indicated type, a compile-time error occurs.</span> </span><span class="locator">
Paragraph 4</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P4S1"></a>The value of a real literal having type <span class="keyword">float</span> or <span class="keyword">double</span> is determined by using the IEEE "round to nearest" mode.</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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