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📁 This ECMA Standard specifies the form and establishes the interpretation of programs written in the
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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="14.6.5.htm"><img src="previous.gif" alt="previous" border="0" /></a><a href="14.7.htm"><img src="next.gif" alt="next" border="0" /></a></span><span class="clause-depth"><a href="13.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="15.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number-link"><a href="14.htm">14</a></span><span class="clause-title-previous"> Expressions</span></span><span class="clause-depth"><a href="14.5.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="14.7.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number-link"><a href="14.6.htm">14.6</a></span><span class="clause-title-previous"> Unary expressions</span></span><span class="clause-depth"><a href="14.6.5.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="14.6.6.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number">14.6.6</span><span class="clause-title"> Cast expressions</span></span><span class="locator">
     Paragraph 1</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P1S1"></a>A <span class="non-terminal"><a href="14.6.6.htm#cast-expression">cast-expression</a></span> is used to explicitly convert an expression to a given type.</span> <span class="grammar-production"><span class="name"><a name="cast-expression"></a>cast-expression</span> : <span class="rhs"><span class="terminal">(</span> <span class="non-terminal"><a href="11.htm#type">type</a></span> <span class="terminal">)</span> <span class="non-terminal"><a href="14.6.htm#unary-expression">unary-expression</a></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>A <span class="non-terminal"><a href="14.6.6.htm#cast-expression">cast-expression</a></span> of the form (T)E, where T is a type and E is a <span class="non-terminal"><a href="14.6.htm#unary-expression">unary-expression</a></span>, performs an explicit conversion (<a href="13.2.htm">&#167;13.2</a>) of the value of E to type T.</span> <span class="sentence"><span class="sentence-number">2</span> <a name="P2S2"></a>If no explicit conversion exists from the type of E to T, a compile-time error occurs.</span> <span class="sentence"><span class="sentence-number">3</span> <a name="P2S3"></a>Otherwise, the result is the value produced by the explicit conversion.</span> <span class="sentence"><span class="sentence-number">4</span> <a name="P2S4"></a>The result is always classified as a value, even if E denotes a variable.</span> </span><span class="locator">
     Paragraph 3</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P3S1"></a>The grammar for a <span class="non-terminal"><a href="14.6.6.htm#cast-expression">cast-expression</a></span> leads to certain syntactic ambiguities.</span> <span class="sentence"><span class="sentence-number">2</span> <a name="P3S2"></a>For example, the expression  (x)-y could either be interpreted as a <span class="non-terminal"><a href="14.6.6.htm#cast-expression">cast-expression</a></span> (a cast of -y to type x) or as an <span class="non-terminal"><a href="14.7.htm#additive-expression">additive-expression</a></span> combined with a <span class="non-terminal"><a href="14.5.3.htm#parenthesized-expression">parenthesized-expression</a></span> (which computes the value x  -y).</span> </span><span class="locator">
     Paragraph 4</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P4S1"></a>To resolve <span class="non-terminal"><a href="14.6.6.htm#cast-expression">cast-expression</a></span> ambiguities, the following rule exists: A sequence of one or more tokens (<a href="9.4.htm">&#167;9.4</a>) enclosed in parentheses is considered the start of a <span class="non-terminal"><a href="14.6.6.htm#cast-expression">cast-expression</a></span> only if at least one of the following are true: </span><ul><li><span class="sentence"><span class="sentence-number">2</span> <a name="P4S2"></a> The sequence of tokens is correct grammar for a type, but not for an expression.</span> </li><li><span class="sentence"><span class="sentence-number">3</span> <a name="P4S3"></a> The sequence of tokens is correct grammar for a type, and the token immediately following the closing parentheses is the token "~", the token "!", the token "(", an identifier (<a href="9.4.1.htm">&#167;9.4.1</a>), a literal (<a href="9.4.4.htm">&#167;9.4.4</a>), or any keyword (<a href="9.4.3.htm">&#167;9.4.3</a>) except as and is.</span> </li></ul></span><span class="paragraph"><span class="note">[Note: The above rule means that only if the construct is unambiguously a <span class="non-terminal"><a href="14.6.6.htm#cast-expression">cast-expression</a></span> is it considered a <span class="non-terminal"><a href="14.6.6.htm#cast-expression">cast-expression</a></span>. end note]</span> </span><span class="locator">
     Paragraph 5</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P5S1"></a>The term "correct grammar" above means only that the sequence of tokens must conform to the particular grammatical production.</span> <span class="sentence"><span class="sentence-number">2</span> <a name="P5S2"></a>It specifically does not consider the actual meaning of any constituent identifiers.</span> <span class="sentence"><span class="sentence-number">3</span> <a name="P5S3"></a>For example, if x and y are identifiers, then x.y is correct grammar for a type, even if x.y doesn't actually denote a type.</span> </span><span class="paragraph"><span class="note">[Note: From the disambiguation rule, it follows that, if x and y are identifiers, (x)y, (x)(y), and (x)(-y) are <span class="non-terminal"><a href="14.6.6.htm#cast-expression">cast-expression</a></span>s, but (x)-y is not, even if x identifies a type. However, if x is a keyword that identifies a predefined type (such as <span class="keyword">int</span>), then all four forms are <span class="non-terminal"><a href="14.6.6.htm#cast-expression">cast-expression</a></span>s (because such a keyword could not possibly be an expression by itself). end note]</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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