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<html><!-- #BeginTemplate "/Templates/tmpl.dwt" --><!-- DW6 --><head><!-- #BeginEditable "doctitle" --> <title>PTypes: string: operators</title><!-- #EndEditable --> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link rel="stylesheet" href="styles.css"></head><body bgcolor="#FFFFFF" leftmargin="40" marginwidth="40"><p><a href="../index.html"><img src="title-20.png" width="253" height="39" alt="C++ Portable Types Library (PTypes) Version 2.0" border="0"></a> <hr size="1" noshade><!-- #BeginEditable "body" --> <p class="hpath"><a href="index.html">Top</a>: <a href="basic.html">Basic types</a>: <a href="string.html">string</a>: Operators</p><blockquote> <pre class="lang">#include <ptypes.h>class string {<span class="comment"> // assignment</span> string& operator =(const char*); string& operator =(char); string& operator =(const string&); friend void assign(string&, const char* buf, int len);<span class="comment"> // concatenation</span> string& operator +=(const char*); string& operator +=(char); string& operator +=(const string&); string operator +(const char*) const; string operator +(char) const; string operator +(const string&) const; friend string operator +(const char*, const string&); friend string operator +(char c, const string&);<span class="comment"> // comparison</span> bool operator ==(const char*) const; bool operator ==(char) const; bool operator ==(const string&) const; bool operator !=(const char*) const; bool operator !=(char c) const; bool operator !=(const string&) const;<span class="comment"> // indexed character access, 0-based</span> char& string::operator[] (int index); const char& string::operator[] (int index) const;}</pre></blockquote><p>The string class defines the following binary operators: assignment (<span class="lang">=</span>), concatenation (<span class="lang">+</span>), concatenation with assignment (<span class="lang">+=</span>) and comparison (<span class="lang">==</span>,<span class="lang"> !=</span>). At least one of the operands (either left or right) must be of type <span class="lang">string</span>. Another operand can be one of the following: <span class="lang">char</span>, <span class="lang">char*</span> or <span class="lang">string</span>.</p><p>Indexed access operator allows to store or retrieve a value of an individual character. The index is 0-based. When compiled with either <span class="lang">DEBUG</span> or <span class="lang">CHECK_BOUNDS</span> conditional symbol, bounds checking is performed for the indexed access; if the index is out of bounds (i.e. less than 0 or equals to or greater than the length of the string), an unrecoverable error is raised. The non-debugging version of the library never checks for index overlfows, thus making your program somewhat faster but less safe.</p><p><b>Examples</b></p><blockquote> <pre>string s1 = "abc", s2 = 'd', s3;s3 = s1 + s2;s2 += "ef";s3[2] = 'B';</pre></blockquote><p class="seealso">See also: <a href="string.constructors.html">Constructors/destructors</a>, <a href="string.typecasts.html">Typecasts</a>, <a href="string.manipulation.html">Manipulation</a>, <a href="string.conversion.html">Conversion</a></p><!-- #EndEditable --><hr size="1"><a href="../index.html" class="ns">PTypes home</a></body><!-- #EndTemplate --></html>⌨️ 快捷键说明
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