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| Next: <a href="C-Plus-Plus-Expressions.html#C-Plus-Plus-Expressions" accesskey="n" rel="next">C Plus Plus Expressions</a>, Previous: <a href="C-Operators.html#C-Operators" accesskey="p" rel="prev">C Operators</a>, Up: <a href="C.html#C" accesskey="u" rel="up">C</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p> |
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| <a name="C-and-C_002b_002b-Constants"></a> |
| <h4 class="subsubsection">15.4.1.2 C and C<tt>++</tt> Constants</h4> |
| |
| <a name="index-C-and-C_002b_002b-constants"></a> |
| |
| <p><small>GDB</small> allows you to express the constants of C and C<tt>++</tt> in the |
| following ways: |
| </p> |
| <ul> |
| <li> Integer constants are a sequence of digits. Octal constants are |
| specified by a leading ‘<samp>0</samp>’ (i.e. zero), and hexadecimal constants |
| by a leading ‘<samp>0x</samp>’ or ‘<samp>0X</samp>’. Constants may also end with a letter |
| ‘<samp>l</samp>’, specifying that the constant should be treated as a |
| <code>long</code> value. |
| |
| </li><li> Floating point constants are a sequence of digits, followed by a decimal |
| point, followed by a sequence of digits, and optionally followed by an |
| exponent. An exponent is of the form: |
| ‘<samp>e<span class="roman">[[</span>+<span class="roman">]|</span><span class="nolinebreak">-</span><span class="roman">]</span><var>nnn</var><!-- /@w --></samp>’, where <var>nnn</var> is another |
| sequence of digits. The ‘<samp>+</samp>’ is optional for positive exponents. |
| A floating-point constant may also end with a letter ‘<samp>f</samp>’ or |
| ‘<samp>F</samp>’, specifying that the constant should be treated as being of |
| the <code>float</code> (as opposed to the default <code>double</code>) type; or with |
| a letter ‘<samp>l</samp>’ or ‘<samp>L</samp>’, which specifies a <code>long double</code> |
| constant. |
| |
| </li><li> Enumerated constants consist of enumerated identifiers, or their |
| integral equivalents. |
| |
| </li><li> Character constants are a single character surrounded by single quotes |
| (<code>'</code>), or a number—the ordinal value of the corresponding character |
| (usually its <small>ASCII</small> value). Within quotes, the single character may |
| be represented by a letter or by <em>escape sequences</em>, which are of |
| the form ‘<samp>\<var>nnn</var></samp>’, where <var>nnn</var> is the octal representation |
| of the character’s ordinal value; or of the form ‘<samp>\<var>x</var></samp>’, where |
| ‘<samp><var>x</var></samp>’ is a predefined special character—for example, |
| ‘<samp>\n</samp>’ for newline. |
| |
| <p>Wide character constants can be written by prefixing a character |
| constant with ‘<samp>L</samp>’, as in C. For example, ‘<samp>L'x'</samp>’ is the wide |
| form of ‘<samp>x</samp>’. The target wide character set is used when |
| computing the value of this constant (see <a href="Character-Sets.html#Character-Sets">Character Sets</a>). |
| </p> |
| </li><li> String constants are a sequence of character constants surrounded by |
| double quotes (<code>"</code>). Any valid character constant (as described |
| above) may appear. Double quotes within the string must be preceded by |
| a backslash, so for instance ‘<samp>"a\"b'c"</samp>’ is a string of five |
| characters. |
| |
| <p>Wide string constants can be written by prefixing a string constant |
| with ‘<samp>L</samp>’, as in C. The target wide character set is used when |
| computing the value of this constant (see <a href="Character-Sets.html#Character-Sets">Character Sets</a>). |
| </p> |
| </li><li> Pointer constants are an integral value. You can also write pointers |
| to constants using the C operator ‘<samp>&</samp>’. |
| |
| </li><li> Array constants are comma-separated lists surrounded by braces ‘<samp>{</samp>’ |
| and ‘<samp>}</samp>’; for example, ‘<samp>{1,2,3}</samp>’ is a three-element array of |
| integers, ‘<samp>{{1,2}, {3,4}, {5,6}}</samp>’ is a three-by-two array, |
| and ‘<samp>{&"hi", &"there", &"fred"}</samp>’ is a three-element array of pointers. |
| </li></ul> |
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