| <html> |
| <head> |
| <title>Character Sets</title> |
| <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> |
| <link rel="stylesheet" href="theme/style.css" type="text/css"> |
| </head> |
| |
| <body> |
| <table width="100%" border="0" background="theme/bkd2.gif" cellspacing="2"> |
| <tr> |
| <td width="10"> |
| </td> |
| <td width="85%"> |
| <font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Character Sets</b></font> |
| </td> |
| <td width="112"><a href="http://spirit.sf.net"><img src="theme/spirit.gif" width="112" height="48" align="right" border="0"></a></td> |
| </tr> |
| </table> |
| <br> |
| <table border="0"> |
| <tr> |
| <td width="10"></td> |
| <td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td> |
| <td width="30"><a href="loops.html"><img src="theme/l_arr.gif" border="0"></a></td> |
| <td width="30"><a href="confix.html"><img src="theme/r_arr.gif" border="0"></a></td> |
| </tr> |
| </table> |
| <p>The character set <tt>chset</tt> matches a set of characters over a finite |
| range bounded by the limits of its template parameter <tt>CharT</tt>. This class |
| is an optimization of a parser that acts on a set of single characters. The |
| template class is parameterized by the character type <tt>CharT</tt> and can |
| work efficiently with 8, 16 and 32 and even 64 bit characters.</p> |
| <pre><span class=identifier> </span><span class=keyword>template </span><span class=special><</span><span class=keyword>typename </span><span class=identifier>CharT </span><span class=special>= </span><span class=keyword>char</span><span class=special>> |
| </span><span class=keyword>class </span><span class=identifier>chset</span><span class=special>;</span></pre> |
| <p>The <tt>chset</tt> is constructed from literals (e.g. <tt>'x'</tt>), <tt>ch_p</tt> |
| or <tt>chlit<></tt>, <tt>range_p</tt> or <tt>range<></tt>, <tt>anychar_p</tt> |
| and <tt>nothing_p</tt> (see <a href="primitives.html">primitives</a>) or copy-constructed |
| from another <tt>chset</tt>. The <tt>chset</tt> class uses a copy-on-write scheme |
| that enables instances to be passed along easily by value.</p> |
| <table width="80%" border="0" align="center"> |
| <tr> |
| <td class="note_box"><img src="theme/lens.gif" width="15" height="16"> <b>Sparse |
| bit vectors</b><br> |
| <br> |
| To accomodate 16/32 and 64 bit characters, the <tt>chset</tt> class |
| statically switches from a <tt>std::bitset</tt> implementation when the |
| character type is not greater than 8 bits, to a sparse bit/boolean set which |
| uses a sorted vector of disjoint ranges (<tt>range_run</tt>). The set is |
| constructed from ranges such that adjacent or overlapping ranges are coalesced.<br> |
| <br> |
| range_runs are very space-economical in situations where there are lots |
| of ranges and a few individual disjoint values. Searching is O(log n) where |
| n is the number of ranges.</td> |
| </tr> |
| </table> |
| <p> Examples:<br> |
| </p> |
| <pre><span class=identifier> </span><span class=identifier>chset</span><span class=special><> </span><span class=identifier>s1</span><span class=special>(</span><span class=literal>'x'</span><span class=special>); |
| </span><span class=identifier>chset</span><span class=special><> </span><span class=identifier>s2</span><span class=special>(</span><span class=identifier>anychar_p </span><span class=special>- </span><span class=identifier>s1</span><span class=special>);</span></pre> |
| <p>Optionally, character sets may also be constructed using a definition string |
| following a syntax that resembles posix style regular expression character sets, |
| except that double quotes delimit the set elements instead of square brackets |
| and there is no special negation <tt>^</tt> character.</p> |
| <pre> <span class=identifier>range </span><span class=special>= </span><span class=identifier>anychar_p </span><span class=special>>> </span><span class=literal>'-' </span><span class=special>>> </span><span class=identifier>anychar_p</span><span class=special>; |
| </span><span class=identifier>set </span><span class=special>= *(</span><span class=identifier>range_p </span><span class=special>| </span><span class=identifier>anychar_p</span><span class=special>);</span></pre> |
| <p>Since we are defining the set using a C string, the usual C/C++ literal string |
| syntax rules apply. Examples:<br> |
| </p> |
| <pre> <span class=identifier>chset</span><span class=special><> </span><span class=identifier>s1</span><span class=special>(</span><span class=string>"a-zA-Z"</span><span class=special>); </span><span class=comment>// alphabetic characters |
| </span><span class=identifier>chset</span><span class=special><> </span><span class=identifier>s2</span><span class=special>(</span><span class=string>"0-9a-fA-F"</span><span class=special>); </span><span class=comment>// hexadecimal characters |
| </span><span class=identifier>chset</span><span class=special><> </span><span class=identifier>s3</span><span class=special>(</span><span class=string>"actgACTG"</span><span class=special>); </span><span class=comment>// DNA identifiers |
| </span><span class=identifier>chset</span><span class=special><> </span><span class=identifier>s4</span><span class=special>(</span><span class=string>"\x7f\x7e"</span><span class=special>); </span><span class=comment>// Hexadecimal 0x7F and 0x7E</span></pre> |
| <p>The standard Spirit set operators apply (see <a href="operators.html">operators</a>) |
| plus an additional character-set-specific inverse (negation <tt>~</tt>) operator:<span class=comment></span></p> |
| |
| <table width="90%" border="0" align="center"> |
| <tr> |
| <td class="table_title" colspan="2">Character set operators</td> |
| </tr> |
| <tr> |
| <td class="table_cells" width="28%"><b>~a</b></td> |
| <td class="table_cells" width="72%">Set inverse</td> |
| </tr> |
| <tr> |
| <td class="table_cells" width="28%"><b>a | b</b></td> |
| <td class="table_cells" width="72%">Set union</td> |
| </tr> |
| <tr> |
| <td class="table_cells" width="28%"><b>a & </b></td> |
| <td class="table_cells" width="72%">Set intersection</td> |
| </tr> |
| <tr> |
| <td class="table_cells" width="28%"><b>a - b</b></td> |
| <td class="table_cells" width="72%">Set difference</td> |
| </tr> |
| <tr> |
| <td class="table_cells" width="28%"><b>a ^ b</b></td> |
| <td class="table_cells" width="72%">Set xor</td> |
| </tr> |
| </table> |
| <p></p> |
| <p></p> |
| <p></p> |
| <p></p> |
| <p></p> |
| <p></p> |
| <p></p> |
| <p></p> |
| <p>where operands a and b are both <tt>chsets</tt> or one of the operand is either |
| a literal character, <tt>ch_p</tt> or <tt>chlit</tt>, <tt>range_p</tt> or <tt>range</tt>, |
| <tt>anychar_p</tt> or <tt>nothing_p</tt>. Special optimized overloads are provided |
| for <tt>anychar_p</tt> and <tt>nothing_p</tt> operands. A <tt>nothing_p</tt> |
| operand is converted to an empty set, while an <tt>anychar_p</tt> operand is |
| converted to a set having elements of the full range of the character type used |
| (e.g. 0-255 for unsigned 8 bit chars).</p> |
| <p>A special case is <tt>~anychar_p</tt> which yields <tt>nothing_p</tt>, but |
| <tt>~nothing_p</tt> is illegal. Inversion of <tt>anychar_p</tt> is asymmetrical, |
| a one-way trip comparable to converting <tt>T*</tt> to a <tt>void*.</tt></p> |
| <table width="90%" border="0" align="center"> |
| <tr> |
| <td class="table_title" colspan="2">Special conversions</td> |
| </tr> |
| <tr> |
| <td class="table_cells" width="28%"><b>chset<CharT>(nothing_p)</b></td> |
| <td class="table_cells" width="72%">empty set</td> |
| </tr> |
| <tr> |
| <td class="table_cells" width="28%"><b>chset<CharT>(anychar_p)</b></td> |
| <td class="table_cells" width="72%">full range of CharT (e.g. 0-255 for unsigned |
| 8 bit chars)</td> |
| </tr> |
| <tr> |
| <td class="table_cells" width="28%"><b>~anychar_p</b></td> |
| <td class="table_cells" width="72%">nothing_p</td> |
| </tr> |
| <tr> |
| <td class="table_cells" width="28%"><b>~nothing_p</b></td> |
| <td class="table_cells" width="72%">illegal</td> |
| </tr> |
| </table> |
| |
| <p></p><table border="0"> |
| <tr> |
| <td width="10"></td> |
| <td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td> |
| <td width="30"><a href="loops.html"><img src="theme/l_arr.gif" border="0"></a></td> |
| <td width="30"><a href="confix.html"><img src="theme/r_arr.gif" border="0"></a></td> |
| </tr> |
| </table> |
| <br> |
| <hr size="1"> |
| <p class="copyright">Copyright © 1998-2003 Joel de Guzman<br> |
| <br> |
| <font size="2">Use, modification and distribution is subject to the Boost Software |
| License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at |
| http://www.boost.org/LICENSE_1_0.txt) </font> </p> |
| </body> |
| </html> |
