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| author | Anas Nashif <anas.nashif@intel.com> | 2012-10-30 12:57:26 -0700 |
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| committer | Anas Nashif <anas.nashif@intel.com> | 2012-10-30 12:57:26 -0700 |
| commit | 1a78a62555be32868418fe52f8e330c9d0f95d5a (patch) | |
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diff --git a/doc/html/string_algo/usage.html b/doc/html/string_algo/usage.html new file mode 100755 index 0000000000..e9588ca24e --- /dev/null +++ b/doc/html/string_algo/usage.html @@ -0,0 +1,389 @@ +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> +<title>Usage</title> +<link rel="stylesheet" href="../../../doc/src/boostbook.css" type="text/css"> +<meta name="generator" content="DocBook XSL Stylesheets V1.76.1"> +<link rel="home" href="../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> +<link rel="up" href="../string_algo.html" title="Chapter 27. Boost String Algorithms Library"> +<link rel="prev" href="release_notes.html" title="Release Notes"> +<link rel="next" href="quickref.html" title="Quick Reference"> +</head> +<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> +<table cellpadding="2" width="100%"><tr> +<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../boost.png"></td> +<td align="center"><a href="../../../index.html">Home</a></td> +<td align="center"><a href="../../../libs/libraries.htm">Libraries</a></td> +<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> +<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> +<td align="center"><a href="../../../more/index.htm">More</a></td> +</tr></table> +<hr> +<div class="spirit-nav"> +<a accesskey="p" href="release_notes.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../string_algo.html"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="quickref.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> +</div> +<div class="section"> +<div class="titlepage"><div><div><h2 class="title" style="clear: both"> +<a name="string_algo.usage"></a>Usage</h2></div></div></div> +<div class="toc"><dl> +<dt><span class="section"><a href="usage.html#id3183270">First Example</a></span></dt> +<dt><span class="section"><a href="usage.html#id3183468">Case conversion</a></span></dt> +<dt><span class="section"><a href="usage.html#id3183534">Predicates and Classification</a></span></dt> +<dt><span class="section"><a href="usage.html#id3183616">Trimming</a></span></dt> +<dt><span class="section"><a href="usage.html#id3183685">Find algorithms</a></span></dt> +<dt><span class="section"><a href="usage.html#id3183806">Replace Algorithms</a></span></dt> +<dt><span class="section"><a href="usage.html#id3183933">Find Iterator</a></span></dt> +<dt><span class="section"><a href="usage.html#id3184031">Split</a></span></dt> +</dl></div> +<div class="section"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="id3183270"></a>First Example</h3></div></div></div> +<p> + Using the algorithms is straightforward. Let us have a look at the first example: + </p> +<pre class="programlisting"> + #include <boost/algorithm/string.hpp> + using namespace std; + using namespace boost; + + // ... + + string str1(" hello world! "); + to_upper(str1); // str1 == " HELLO WORLD! " + trim(str1); // str1 == "HELLO WORLD!" + + string str2= + to_lower_copy( + ireplace_first_copy( + str1,"hello","goodbye")); // str2 == "goodbye world!" + </pre> +<p> + This example converts str1 to upper case and trims spaces from the start and the end + of the string. str2 is then created as a copy of str1 with "hello" replaced with "goodbye". + This example demonstrates several important concepts used in the library: + </p> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"> +<li class="listitem"> +<p><span class="bold"><strong>Container parameters:</strong></span> + Unlike in the STL algorithms, parameters are not specified only in the form + of iterators. The STL convention allows for great flexibility, + but it has several limitations. It is not possible to <span class="emphasis"><em>stack</em></span> algorithms together, + because a container is passed in two parameters. Therefore it is not possible to use + a return value from another algorithm. It is considerably easier to write + <code class="computeroutput">to_lower(str1)</code>, than <code class="computeroutput">to_lower(str1.begin(), str1.end())</code>. + </p> +<p> + The magic of <a href="../../../libs/range/index.html" target="_top">Boost.Range</a> + provides a uniform way of handling different string types. + If there is a need to pass a pair of iterators, + <a href="../../../libs/range/doc/html/range/reference/utilities/iterator_range.html" target="_top"><code class="computeroutput">boost::iterator_range</code></a> + can be used to package iterators into a structure with a compatible interface. + </p> +</li> +<li class="listitem"><p><span class="bold"><strong>Copy vs. Mutable:</strong></span> + Many algorithms in the library are performing a transformation of the input. + The transformation can be done in-place, mutating the input sequence, or a copy + of the transformed input can be created, leaving the input intact. None of + these possibilities is superior to the other one and both have different + advantages and disadvantages. For this reason, both are provided with the library. + </p></li> +<li class="listitem"><p><span class="bold"><strong>Algorithm stacking:</strong></span> + Copy versions return a transformed input as a result, thus allow a simple chaining of + transformations within one expression (i.e. one can write <code class="computeroutput">trim_copy(to_upper_copy(s))</code>). + Mutable versions have <code class="computeroutput">void</code> return, to avoid misuse. + </p></li> +<li class="listitem"><p><span class="bold"><strong>Naming:</strong></span> + Naming follows the conventions from the Standard C++ Library. If there is a + copy and a mutable version of the same algorithm, the mutable version has no suffix + and the copy version has the suffix <span class="emphasis"><em>_copy</em></span>. + Some algorithms have the prefix <span class="emphasis"><em>i</em></span> + (e.g. <code class="computeroutput"><a class="link" href="../boost/algorithm/ifind_first.html" title="Function template ifind_first">ifind_first()</a></code>). + This prefix identifies that the algorithm works in a case-insensitive manner. + </p></li> +</ul></div> +<p> + To use the library, include the <code class="computeroutput"><a class="link" href="reference.html#header.boost.algorithm.string_hpp" title="Header <boost/algorithm/string.hpp>">boost/algorithm/string.hpp</a></code> header. + If the regex related functions are needed, include the + <code class="computeroutput"><a class="link" href="reference.html#header.boost.algorithm.string_regex_hpp" title="Header <boost/algorithm/string_regex.hpp>">boost/algorithm/string_regex.hpp</a></code> header. + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="id3183468"></a>Case conversion</h3></div></div></div> +<p> + STL has a nice way of converting character case. Unfortunately, it works only + for a single character and we want to convert a string, + </p> +<pre class="programlisting"> + string str1("HeLlO WoRld!"); + to_upper(str1); // str1=="HELLO WORLD!" + </pre> +<p> + <code class="computeroutput"><a class="link" href="../boost/algorithm/to_upper.html" title="Function template to_upper">to_upper()</a></code> and <code class="computeroutput"><a class="link" href="../boost/algorithm/to_lower.html" title="Function template to_lower">to_lower()</a></code> convert the case of + characters in a string using a specified locale. + </p> +<p> + For more information see the reference for <code class="computeroutput"><a class="link" href="reference.html#header.boost.algorithm.string.case_conv_hpp" title="Header <boost/algorithm/string/case_conv.hpp>">boost/algorithm/string/case_conv.hpp</a></code>. + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="id3183534"></a>Predicates and Classification</h3></div></div></div> +<p> + A part of the library deals with string related predicates. Consider this example: + </p> +<pre class="programlisting"> + bool is_executable( string& filename ) + { + return + iends_with(filename, ".exe") || + iends_with(filename, ".com"); + } + + // ... + string str1("command.com"); + cout + << str1 + << (is_executable("command.com")? "is": "is not") + << "an executable" + << endl; // prints "command.com is an executable" + + //.. + char text1[]="hello world!"; + cout + << text1 + << (all( text1, is_lower() )? "is": "is not") + << " written in the lower case" + << endl; // prints "hello world! is written in the lower case" + </pre> +<p> + The predicates determine whether if a substring is contained in the input string + under various conditions. The conditions are: a string starts with the substring, + ends with the substring, + simply contains the substring or if both strings are equal. See the reference for + <code class="computeroutput"><a class="link" href="reference.html#header.boost.algorithm.string.predicate_hpp" title="Header <boost/algorithm/string/predicate.hpp>">boost/algorithm/string/predicate.hpp</a></code> for more details. + </p> +<p> + In addition the algorithm <code class="computeroutput"><a class="link" href="../boost/algorithm/all.html" title="Function template all">all()</a></code> checks + all elements of a container to satisfy a condition specified by a predicate. + This predicate can be any unary predicate, but the library provides a bunch of + useful string-related predicates and combinators ready for use. + These are located in the <code class="computeroutput"><a class="link" href="reference.html#header.boost.algorithm.string.classification_hpp" title="Header <boost/algorithm/string/classification.hpp>">boost/algorithm/string/classification.hpp</a></code> header. + Classification predicates can be combined using logical combinators to form + a more complex expressions. For example: <code class="computeroutput">is_from_range('a','z') || is_digit()</code> + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="id3183616"></a>Trimming</h3></div></div></div> +<p> + When parsing the input from a user, strings usually have unwanted leading or trailing + characters. To get rid of them, we need trim functions: + </p> +<pre class="programlisting"> + string str1=" hello world! "; + string str2=trim_left_copy(str1); // str2 == "hello world! " + string str3=trim_right_copy(str1); // str3 == " hello world!" + trim(str1); // str1 == "hello world!" + + string phone="00423333444"; + // remove leading 0 from the phone number + trim_left_if(phone,is_any_of("0")); // phone == "423333444" + </pre> +<p> + It is possible to trim the spaces on the right, on the left or on both sides of a string. + And for those cases when there is a need to remove something else than blank space, there + are <span class="emphasis"><em>_if</em></span> variants. Using these, a user can specify a functor which will + select the <span class="emphasis"><em>space</em></span> to be removed. It is possible to use classification + predicates like <code class="computeroutput"><a class="link" href="../boost/algorithm/is_digit.html" title="Function is_digit">is_digit()</a></code> mentioned in the previous paragraph. + See the reference for the <code class="computeroutput"><a class="link" href="reference.html#header.boost.algorithm.string.trim_hpp" title="Header <boost/algorithm/string/trim.hpp>">boost/algorithm/string/trim.hpp</a></code>. + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="id3183685"></a>Find algorithms</h3></div></div></div> +<p> + The library contains a set of find algorithms. Here is an example: + </p> +<pre class="programlisting"> + char text[]="hello dolly!"; + iterator_range<char*> result=find_last(text,"ll"); + + transform( result.begin(), result.end(), result.begin(), bind2nd(plus<char>(), 1) ); + // text = "hello dommy!" + + to_upper(result); // text == "hello doMMy!" + + // iterator_range is convertible to bool + if(find_first(text, "dolly")) + { + cout << "Dolly is there" << endl; + } + </pre> +<p> + We have used <code class="computeroutput"><a class="link" href="../boost/algorithm/find_last.html" title="Function template find_last">find_last()</a></code> to search the <code class="computeroutput">text</code> for "ll". + The result is given in the <a href="../../../libs/range/doc/html/range/reference/utilities/iterator_range.html" target="_top"><code class="computeroutput">boost::iterator_range</code></a>. + This range delimits the + part of the input which satisfies the find criteria. In our example it is the last occurrence of "ll". + + As we can see, input of the <code class="computeroutput"><a class="link" href="../boost/algorithm/find_last.html" title="Function template find_last">find_last()</a></code> algorithm can be also + char[] because this type is supported by + <a href="../../../libs/range/index.html" target="_top">Boost.Range</a>. + + The following lines transform the result. Notice that + <a href="../../../libs/range/doc/html/range/reference/utilities/iterator_range.html" target="_top"><code class="computeroutput">boost::iterator_range</code></a> has familiar + <code class="computeroutput">begin()</code> and <code class="computeroutput">end()</code> methods, so it can be used like any other STL container. + Also it is convertible to bool therefore it is easy to use find algorithms for a simple containment checking. + </p> +<p> + Find algorithms are located in <code class="computeroutput"><a class="link" href="reference.html#header.boost.algorithm.string.find_hpp" title="Header <boost/algorithm/string/find.hpp>">boost/algorithm/string/find.hpp</a></code>. + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="id3183806"></a>Replace Algorithms</h3></div></div></div> +<p> + Find algorithms can be used for searching for a specific part of string. Replace goes one step + further. After a matching part is found, it is substituted with something else. The substitution is computed + from the original, using some transformation. + </p> +<pre class="programlisting"> + string str1="Hello Dolly, Hello World!" + replace_first(str1, "Dolly", "Jane"); // str1 == "Hello Jane, Hello World!" + replace_last(str1, "Hello", "Goodbye"); // str1 == "Hello Jane, Goodbye World!" + erase_all(str1, " "); // str1 == "HelloJane,GoodbyeWorld!" + erase_head(str1, 6); // str1 == "Jane,GoodbyeWorld!" + </pre> +<p> + For the complete list of replace and erase functions see the + <a class="link" href="reference.html" title="Reference">reference</a>. + There is a lot of predefined function for common usage, however, the library allows you to + define a custom <code class="computeroutput">replace()</code> that suits a specific need. There is a generic <code class="computeroutput"><a class="link" href="../boost/algorithm/find_format.html" title="Function template find_format">find_format()</a></code> + function which takes two parameters. + The first one is a <a class="link" href="concept.html#string_algo.finder_concept" title="Finder Concept">Finder</a> object, the second one is + a <a class="link" href="concept.html#string_algo.formatter_concept" title="Formatter concept">Formatter</a> object. + The Finder object is a functor which performs the searching for the replacement part. The Formatter object + takes the result of the Finder (usually a reference to the found substring) and creates a + substitute for it. Replace algorithm puts these two together and makes the desired substitution. + </p> +<p> + Check <code class="computeroutput"><a class="link" href="reference.html#header.boost.algorithm.string.replace_hpp" title="Header <boost/algorithm/string/replace.hpp>">boost/algorithm/string/replace.hpp</a></code>, <code class="computeroutput"><a class="link" href="reference.html#header.boost.algorithm.string.erase_hpp" title="Header <boost/algorithm/string/erase.hpp>">boost/algorithm/string/erase.hpp</a></code> and + <code class="computeroutput"><a class="link" href="reference.html#header.boost.algorithm.string.find_format_hpp" title="Header <boost/algorithm/string/find_format.hpp>">boost/algorithm/string/find_format.hpp</a></code> for reference. + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="id3183933"></a>Find Iterator</h3></div></div></div> +<p> + An extension to find algorithms it the Find Iterator. Instead of searching for just a one part of a string, + the find iterator allows us to iterate over the substrings matching the specified criteria. + This facility is using the <a class="link" href="concept.html#string_algo.finder_concept" title="Finder Concept">Finder</a> to incrementally + search the string. + Dereferencing a find iterator yields an <a href="../../../libs/range/doc/html/range/reference/utilities/iterator_range.html" target="_top"><code class="computeroutput">boost::iterator_range</code></a> + object, that delimits the current match. + </p> +<p> + There are two iterators provided <code class="computeroutput"><a class="link" href="../boost/algorithm/find_iterator.html" title="Class template find_iterator">find_iterator</a></code> and + <code class="computeroutput"><a class="link" href="../boost/algorithm/split_iterator.html" title="Class template split_iterator">split_iterator</a></code>. The former iterates over substrings that are found using the specified + Finder. The latter iterates over the gaps between these substrings. + </p> +<pre class="programlisting"> + string str1("abc-*-ABC-*-aBc"); + // Find all 'abc' substrings (ignoring the case) + // Create a find_iterator + typedef find_iterator<string::iterator> string_find_iterator; + for(string_find_iterator It= + make_find_iterator(str1, first_finder("abc", is_iequal())); + It!=string_find_iterator(); + ++It) + { + cout << copy_range<std::string>(*It) << endl; + } + + // Output will be: + // abc + // ABC + // aBC + + typedef split_iterator<string::iterator> string_split_iterator; + for(string_split_iterator It= + make_split_iterator(str1, first_finder("-*-", is_iequal())); + It!=string_split_iterator(); + ++It) + { + cout << copy_range<std::string>(*It) << endl; + } + + // Output will be: + // abc + // ABC + // aBC + </pre> +<p> + Note that the find iterators have only one template parameter. It is the base iterator type. + The Finder is specified at runtime. This allows us to typedef a find iterator for + common string types and reuse it. Additionally make_*_iterator functions help + to construct a find iterator for a particular range. + </p> +<p> + See the reference in <code class="computeroutput"><a class="link" href="reference.html#header.boost.algorithm.string.find_iterator_hpp" title="Header <boost/algorithm/string/find_iterator.hpp>">boost/algorithm/string/find_iterator.hpp</a></code>. + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="id3184031"></a>Split</h3></div></div></div> +<p> + Split algorithms are an extension to the find iterator for one common usage scenario. + These algorithms use a find iterator and store all matches into the provided + container. This container must be able to hold copies (e.g. <code class="computeroutput">std::string</code>) or + references (e.g. <code class="computeroutput">iterator_range</code>) of the extracted substrings. + </p> +<p> + Two algorithms are provided. <code class="computeroutput"><a class="link" href="../boost/algorithm/find_all.html" title="Function template find_all">find_all()</a></code> finds all copies + of a string in the input. <code class="computeroutput"><a class="link" href="../boost/algorithm/split_id820181.html" title="Function template split">split()</a></code> splits the input into parts. + </p> +<pre class="programlisting"> + string str1("hello abc-*-ABC-*-aBc goodbye"); + + typedef vector< iterator_range<string::iterator> > find_vector_type; + + find_vector_type FindVec; // #1: Search for separators + ifind_all( FindVec, str1, "abc" ); // FindVec == { [abc],[ABC],[aBc] } + + typedef vector< string > split_vector_type; + + split_vector_type SplitVec; // #2: Search for tokens + split( SplitVec, str1, is_any_of("-*"), token_compress_on ); // SplitVec == { "hello abc","ABC","aBc goodbye" } + </pre> +<p> + <code class="computeroutput">[hello]</code> designates an <code class="computeroutput">iterator_range</code> delimiting this substring. + </p> +<p> + First example show how to construct a container to hold references to all extracted + substrings. Algorithm <code class="computeroutput"><a class="link" href="../boost/algorithm/ifind_all.html" title="Function template ifind_all">ifind_all()</a></code> puts into FindVec references + to all substrings that are in case-insensitive manner equal to "abc". + </p> +<p> + Second example uses <code class="computeroutput"><a class="link" href="../boost/algorithm/split_id820181.html" title="Function template split">split()</a></code> to split string str1 into parts + separated by characters '-' or '*'. These parts are then put into the SplitVec. + It is possible to specify if adjacent separators are concatenated or not. + </p> +<p> + More information can be found in the reference: <code class="computeroutput"><a class="link" href="reference.html#header.boost.algorithm.string.split_hpp" title="Header <boost/algorithm/string/split.hpp>">boost/algorithm/string/split.hpp</a></code>. + </p> +</div> +</div> +<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> +<td align="left"><p><small>Last revised: October 30, 2010 at 18:34:45 +0100</small></p></td> +<td align="right"><div class="copyright-footer">Copyright © 2002-2004 Pavol Droba<p>Use, modification and distribution is subject to the Boost + Software License, Version 1.0. (See accompanying file + <code class="filename">LICENSE_1_0.txt</code> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) + </p> +</div></td> +</tr></table> +<hr> +<div class="spirit-nav"> +<a accesskey="p" href="release_notes.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../string_algo.html"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="quickref.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> +</div> +</body> +</html> |