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diff --git a/libstdc++-v3/docs/html/21_strings/howto.html b/libstdc++-v3/docs/html/21_strings/howto.html index 6acd357c959..e49a166c0c5 100644 --- a/libstdc++-v3/docs/html/21_strings/howto.html +++ b/libstdc++-v3/docs/html/21_strings/howto.html @@ -1,13 +1,12 @@ -<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN"> <html> <head> - <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> - <meta name="AUTHOR" content="pme@gcc.gnu.org (Phil Edwards)"> - <meta name="KEYWORDS" content="HOWTO, libstdc++, GCC, g++, libg++, STL"> - <meta name="DESCRIPTION" content="HOWTO for the libstdc++ chapter 21."> - <meta name="GENERATOR" content="vi and eight fingers"> + <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> + <meta name="AUTHOR" content="pme@gcc.gnu.org (Phil Edwards)" /> + <meta name="KEYWORDS" content="HOWTO, libstdc++, GCC, g++, libg++, STL" /> + <meta name="DESCRIPTION" content="HOWTO for the libstdc++ chapter 21." /> + <meta name="GENERATOR" content="vi and eight fingers" /> <title>libstdc++-v3 HOWTO: Chapter 21</title> -<link rel="StyleSheet" href="../lib3styles.css"> +<link rel="StyleSheet" href="../lib3styles.css" /> </head> <body> @@ -18,16 +17,17 @@ <!-- ####################################################### --> -<hr> +<hr /> <h1>Contents</h1> <ul> - <li><a href="#1">MFC's CString</a> - <li><a href="#2">A case-insensitive string class</a> - <li><a href="#3">Breaking a C++ string into tokens</a> - <li><a href="#4">Simple transformations</a> + <li><a href="#1">MFC's CString</a></li> + <li><a href="#2">A case-insensitive string class</a></li> + <li><a href="#3">Breaking a C++ string into tokens</a></li> + <li><a href="#4">Simple transformations</a></li> + <li><a href="#5">Making strings of arbitrary character types</a></li> </ul> -<hr> +<hr /> <!-- ####################################################### --> @@ -42,24 +42,29 @@ <p>Things are not as bad as they seem. In <a href="http://gcc.gnu.org/ml/gcc/1999-04n/msg00236.html">this message</a>, Joe Buck points out a few very important things: + </p> <ul> <li>The Standard <code>string</code> supports all the operations that CString does, with three exceptions. + </li> <li>Two of those exceptions (whitespace trimming and case conversion) are trivial to implement. In fact, we do so on this page. + </li> <li>The third is <code>CString::Format</code>, which allows formatting in the style of <code>sprintf</code>. This deserves some mention: + </li> </ul> - </p> - <a name="1.1internal"> <!-- Coming from Chapter 27 --> - <p>The old libg++ library had a function called form(), which did much + <p><a name="1.1internal"> <!-- Coming from Chapter 27 --> + The old libg++ library had a function called form(), which did much the same thing. But for a Standard solution, you should use the stringstream classes. These are the bridge between the iostream hierarchy and the string class, and they operate with regular streams seamlessly because they inherit from the iostream hierarchy. An quick example: - <pre> + </a> + </p> + <pre> #include <iostream> #include <string> #include <sstream> @@ -79,10 +84,10 @@ return output_stream.str(); } </pre> - </p></a> <p>A serious problem with CString is a design bug in its memory allocation. Specifically, quoting from that same message: - <pre> + </p> + <pre> CString suffers from a common programming error that results in poor performance. Consider the following code: @@ -103,22 +108,25 @@ If you replace CString with string in the above function, the performance is O(n). - </pre> - </p> + </pre> <p>Joe Buck also pointed out some other things to keep in mind when comparing CString and the Standard string class: + </p> <ul> <li>CString permits access to its internal representation; coders who exploited that may have problems moving to <code>string</code>. + </li> <li>Microsoft ships the source to CString (in the files MFC\SRC\Str{core,ex}.cpp), so you could fix the allocation bug and rebuild your MFC libraries. - <em><B>Note:</B> It looks like the the CString shipped with - VC++6.0 has fixed this, although it may in fact have been one - of the VC++ SPs that did it.</em> + <em><strong>Note:</strong> It looks like the the CString shipped + with VC++6.0 has fixed this, although it may in fact have been + one of the VC++ SPs that did it.</em> + </li> <li><code>string</code> operations like this have O(n) complexity <em>if the implementors do it correctly</em>. The libstdc++ implementors did it correctly. Other vendors might not. + </li> <li>While parts of the SGI STL are used in libstdc++-v3, their string class is not. The SGI <code>string</code> is essentially <code>vector<char></code> and does not do any reference @@ -128,13 +136,13 @@ libstdc++ string, the SGI string, and the SGI rope, and this is all before any allocator or traits customizations! (More choices than you can shake a stick at -- want fries with that?) + </li> </ul> - </p> <p>Return <a href="#top">to top of page</a> or <a href="../faq/index.html">to the FAQ</a>. </p> -<hr> +<hr /> <h2><a name="2">A case-insensitive string class</a></h2> <p>The well-known-and-if-it-isn't-well-known-it-ought-to-be <a href="http://www.peerdirect.com/resources/">Guru of the Week</a> @@ -143,7 +151,8 @@ is identical to the standard 'string' class, but is case-insensitive in the same way as the (common but nonstandard) C function stricmp():" - <pre> + </p> + <pre> ci_string s( "AbCdE" ); // case insensitive @@ -153,7 +162,6 @@ // still case-preserving, of course assert( strcmp( s.c_str(), "AbCdE" ) == 0 ); assert( strcmp( s.c_str(), "abcde" ) != 0 ); </pre> - </p> <p>The solution is surprisingly easy. The original answer pages on the GotW website were removed into cold storage, in @@ -188,7 +196,7 @@ <a href="../faq/index.html">to the FAQ</a>. </p> -<hr> +<hr /> <h2><a name="3">Breaking a C++ string into tokens</a></h2> <p>The Standard C (and C++) function <code>strtok()</code> leaves a lot to be desired in terms of user-friendliness. It's unintuitive, it @@ -209,21 +217,23 @@ comments on what kind of string it will accept). The author uses a more general (but less readable) form of it for parsing command strings and the like. If you compiled and ran this code using it: - <pre> + </p> + <pre> std::list<string> ls; stringtok (ls, " this \t is\t\n a test "); for (std::list<string>const_iterator i = ls.begin(); i != ls.end(); ++i) { std::cerr << ':' << (*i) << ":\n"; - }</pre> - You would see this as output: - <pre> + } </pre> + <p>You would see this as output: + </p> + <pre> :this: :is: :a: - :test:</pre> - with all the whitespace removed. The original <code>s</code> is still + :test: </pre> + <p>with all the whitespace removed. The original <code>s</code> is still available for use, <code>ls</code> will clean up after itself, and <code>ls.size()</code> will return how many tokens there were. </p> @@ -247,7 +257,7 @@ <a href="../faq/index.html">to the FAQ</a>. </p> -<hr> +<hr /> <h2><a name="4">Simple transformations</a></h2> <p>Here are Standard, simple, and portable ways to perform common transformations on a <code>string</code> instance, such as "convert @@ -257,7 +267,8 @@ </p> <p>This code will go through some iterations (no pun). Here's the simplistic version usually seen on Usenet: - <pre> + </p> + <pre> #include <string> #include <algorithm> #include <cctype> // old <ctype.h> @@ -275,7 +286,7 @@ std::string capital_s; capital_s.reserve(s.size()); std::transform (s.begin(), s.end(), capital_s.begin(), tolower); </pre> - <span class="larger"><strong>Note</strong></span> that these calls all + <p><span class="larger"><strong>Note</strong></span> that these calls all involve the global C locale through the use of the C functions <code>toupper/tolower</code>. This is absolutely guaranteed to work -- but <em>only</em> if the string contains <em>only</em> characters @@ -286,12 +297,12 @@ characters (hahahahahaha), then you're done. </p> <p>At minimum, you can write short wrappers like - <pre> + </p> + <pre> char toLower (char c) { return tolower(static_cast<unsigned char>(c)); - }</pre> - </p> + } </pre> <p>The correct method is to use a facet for a particular locale and call its conversion functions. These are discussed more in Chapter 22; the specific part is @@ -303,7 +314,8 @@ like transformations, this task is trivial with the use of string's <code>find</code> family. These examples are broken into multiple statements for readability: - <pre> + </p> + <pre> std::string str (" \t blah blah blah \n "); // trim leading whitespace @@ -313,7 +325,7 @@ // trim trailing whitespace notwhite = str.find_last_not_of(" \t\n"); str.erase(notwhite+1); </pre> - Obviously, the calls to <code>find</code> could be inserted directly + <p>Obviously, the calls to <code>find</code> could be inserted directly into the calls to <code>erase</code>, in case your compiler does not optimize named temporaries out of existence. </p> @@ -321,11 +333,20 @@ <a href="../faq/index.html">to the FAQ</a>. </p> +<hr /> +<h2><a name="5">Making strings of arbitrary character types</a></h2> + <p>how to work with char_traits -- in the archives, just need to + go through and pull the examples together + </p> + <p>Return <a href="#top">to top of page</a> or + <a href="../faq/index.html">to the FAQ</a>. + </p> + <!-- ####################################################### --> -<hr> +<hr /> <p class="fineprint"><em> See <a href="../17_intro/license.html">license.html</a> for copying conditions. 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