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Boost-Commit : |
Subject: [Boost-commit] svn:boost r73267 - in trunk: doc/html libs/conversion
From: dnljms_at_[hidden]
Date: 2011-07-21 03:35:30
Author: danieljames
Date: 2011-07-21 03:35:29 EDT (Thu, 21 Jul 2011)
New Revision: 73267
URL: http://svn.boost.org/trac/boost/changeset/73267
Log:
Link up the new lexical cast documentation.
Added:
trunk/doc/html/boost_lexical_cast.html (contents, props changed)
Text files modified:
trunk/libs/conversion/index.html | 2
trunk/libs/conversion/lexical_cast.htm | 362 +--------------------------------------
2 files changed, 12 insertions(+), 352 deletions(-)
Added: trunk/doc/html/boost_lexical_cast.html
==============================================================================
--- (empty file)
+++ trunk/doc/html/boost_lexical_cast.html 2011-07-21 03:35:29 EDT (Thu, 21 Jul 2011)
@@ -0,0 +1,16 @@
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
+<html>
+ <head>
+ <!-- Copyright (C) 2002 Douglas Gregor <doug.gregor -at- gmail.com>
+
+ Distributed under 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) -->
+ <title>Redirect to generated documentation</title>
+ <meta http-equiv="refresh" content="0; URL=http://boost-sandbox.sourceforge.net/doc/html/boost_lexical_cast.html">
+ </head>
+ <body>
+ Automatic redirection failed, please go to
+ http://boost-sandbox.sourceforge.net/doc/html/boost_lexical_cast.html
+ </body>
+</html>
Modified: trunk/libs/conversion/index.html
==============================================================================
--- trunk/libs/conversion/index.html (original)
+++ trunk/libs/conversion/index.html 2011-07-21 03:35:29 EDT (Thu, 21 Jul 2011)
@@ -24,7 +24,7 @@
and <b>polymorphic_downcast<></b> to perform safe casting between
polymorphic types.<br>
</li>
- <li>The boost/lexical_cast header provides <b>lexical_cast<></b>
+ <li>The boost/lexical_cast header provides <b>lexical_cast<></b>
general literal text conversions, such as an <code>int</code> represented as
a <code>string</code>, or vice-versa.</li>
</ul>
Modified: trunk/libs/conversion/lexical_cast.htm
==============================================================================
--- trunk/libs/conversion/lexical_cast.htm (original)
+++ trunk/libs/conversion/lexical_cast.htm 2011-07-21 03:35:29 EDT (Thu, 21 Jul 2011)
@@ -1,356 +1,16 @@
-<!-- saved from url=(0022)http://internet.e-mail -->
-<!doctype html public "-//W3C//DTD HTML Transitional 4.0//EN">
-<html>
- <head>
- <title>lexical_cast</title>
- <meta name="author" content="Kevlin Henney, mailto:kevlin_at_[hidden]">
- <meta name="generator" content="Microsoft FrontPage 5.0">
- </head>
- <body bgcolor="#FFFFFF" text="#000000">
- <h1><img src="../../boost.png" alt="boost.png (6897 bytes)" align="center" width="277" height="86">Header
- boost/lexical_cast.hpp</h1>
- <ul type="square">
- <li>
- Motivation</li>
- <li>
- Examples</li>
- <li>
- Synopsis</li>
- <li>
- lexical_cast</li>
- <li>
- bad_lexical_cast</li>
- <li>
- Frequently Asked Questions</li>
- <li>
- References</li>
- <li>
- Changes</li>
- <li>
- Performance</li>
- </ul>
- <hr>
- <h2><a name="motivation">Motivation</a></h2>
- Sometimes a value must be converted to a literal text form, such as an <code>int</code>
- represented as a <code>string</code>, or vice-versa, when a <code>string</code>
- is interpreted as an <code>int</code>. Such examples are common when converting
- between data types internal to a program and representation external to a
- program, such as windows and configuration files.
- <p>
- The standard C and C++ libraries offer a number of facilities for performing
- such conversions. However, they vary with their ease of use, extensibility, and
- safety.
- <p>
- For instance, there are a number of limitations with the family of standard C
- functions typified by <code>atoi</code>:
- <ul type="square">
- <li>
- Conversion is supported in one direction only: from text to internal data type.
- Converting the other way using the C library requires either the inconvenience
- and compromised safety of the <code>sprintf</code> function, or the loss of
- portability associated with non-standard functions such as <code>itoa</code>.
- </li>
- <li>
- The range of types supported is only a subset of the built-in numeric types,
- namely <code>int</code>, <code>long</code>, and <code>double</code>.
- </li>
- <li>
- The range of types cannot be extended in a uniform manner. For instance,
- conversion from string representation to <code>complex</code> or <code>rational</code>.
- </li>
- </ul>
- The standard C functions typified by <code>strtol</code> have the same basic
- limitations, but offer finer control over the conversion process. However, for
- the common case such control is often either not required or not used. The <code>scanf</code>
- family of functions offer even greater control, but also lack safety and ease
- of use.
- <p>
- The standard C++ library offers <code>stringstream</code> for the kind of
- in-core formatting being discussed. It offers a great deal of control over the
- formatting and conversion of I/O to and from arbitrary types through text.
- However, for simple conversions direct use of <code>stringstream</code> can be
- either clumsy (with the introduction of extra local variables and the loss of
- infix-expression convenience) or obscure (where <code>stringstream</code>
- objects are created as temporary objects in an expression). Facets provide a
- comprehensive concept and facility for controlling textual representation, but
- their perceived complexity and high entry level requires an extreme degree of
- involvement for simple conversions, and excludes all but a few programmers.
- <p>
- The <code>lexical_cast</code> function template offers a convenient and
- consistent form for supporting common conversions to and from arbitrary types
- when they are represented as text. The simplification it offers is in
- expression-level convenience for such conversions. For more involved
- conversions, such as where precision or formatting need tighter control than is
- offered by the default behavior of <code>lexical_cast</code>, the conventional <code>
- stringstream</code> approach is recommended. Where the conversions are
- numeric to numeric, <code>numeric_cast</code>
- may offer more reasonable behavior than <code>lexical_cast</code>.
- <p>
- For a good discussion of the options and issues involved in string-based
- formatting, including comparison of <code>stringstream</code>, <code>lexical_cast</code>,
- and others, see Herb Sutter's article, <a href="http://www.gotw.ca/publications/mill19.htm">
- <i>The String Formatters of Manor Farm</i></a>. Also, take a look at the Performance section.
- <p>
- <hr>
- <h2><a name="examples">Examples</a></h2>
- The following example treats command line arguments as a sequence of numeric
- data: <blockquote>
- <pre>int main(int argc, char * argv[])
-{
- using boost::lexical_cast;
- using boost::bad_lexical_cast;
-
- std::vector<short> args;
-
- while(*++argv)
- {
- try
- {
- args.push_back(lexical_cast<short>(*argv));
- }
- catch(bad_lexical_cast &)
- {
- args.push_back(0);
- }
- }
- ...
-}
-</pre>
- </blockquote>The following example uses numeric data in a string expression: <blockquote>
- <pre>void log_message(const std::string &);
-void log_errno(int yoko)
-{
- log_message("Error " + boost::lexical_cast<std::string>(yoko) + ": " + strerror(yoko));
-}
-</pre>
- </blockquote>
- <hr>
- <h2><a name="synopsis">Synopsis</a></h2>
- Library features defined in "boost/lexical_cast.hpp":
- <blockquote>
- <pre>namespace boost
-{
- class bad_lexical_cast;
- template<typename Target, typename Source>
- Target lexical_cast(const Source& arg);
-}
-</pre>
- </blockquote>Unit test defined in "lexical_cast_test.cpp".
- <p>
- <hr>
- <h2><a name="lexical_cast"><code>lexical_cast</code></a></h2>
- <blockquote>
- <pre>template<typename Target, typename Source>
- Target lexical_cast(const Source& arg);
-</pre>
- </blockquote>Returns the result of streaming <code>arg</code> into a
- standard library string-based stream and then out as a <code>Target</code> object.
- Where <code>Target</code> is either <code>std::string</code>
- or <code>std::wstring</code>, stream extraction takes the whole content
- of the string, including spaces, rather than relying on the default
- <code>operator>></code> behavior.
- If the conversion is unsuccessful, a <a href="#bad_lexical_cast">
- <code>bad_lexical_cast</code></a> exception is thrown.
- <p>
- The requirements on the argument and result types are:
- <ul type="square">
- <li>
- <code>Source</code> is <i>OutputStreamable</i>, meaning that an <code>operator<<</code>
- is defined that takes a <code>std::ostream</code> or <code>std::wostream</code> object on the
- left hand side and an instance of the argument type on the right.
- </li>
- <li>
- <code>Target</code> is <i>InputStreamable</i>, meaning that an <code>operator>></code>
- is defined that takes a <code>std::istream</code> or <code>std::wistream</code> object on the left hand side
- and an instance of the result type on the right.
- </li>
- <li>
- <code>Target</code> is <i>CopyConstructible</i> [20.1.3].
- </li>
- <li>
- <code>Target</code> is <i>DefaultConstructible</i>, meaning that it is possible
- to <i>default-initialize</i> an object of that type [8.5, 20.1.4].
- </li>
- </ul>
- The character type of the underlying stream is assumed to be <code>char</code> unless
- either the <code>Source</code> or the <code>Target</code> requires wide-character
- streaming, in which case the underlying stream uses <code>wchar_t</code>.
- <code>Source</code> types that require wide-character streaming are <code>wchar_t</code>,
- <code>wchar_t *</code>, and <code>std::wstring</code>. <code>Target</code> types that
- require wide-character streaming are <code>wchar_t</code> and <code>std::wstring</code>.
- <p>
- Where a higher degree of control is required over conversions, <code>std::stringstream</code>
- and <code>std::wstringstream</code> offer a more appropriate path. Where non-stream-based conversions are
- required, <code>lexical_cast</code>
- is the wrong tool for the job and is not special-cased for such scenarios.
- <p>
- <hr>
- <h2><a name="bad_lexical_cast"><code>bad_lexical_cast</code></a></h2>
- <blockquote>
- <pre>class bad_lexical_cast : public std::bad_cast
-{
-public:
- ... // <i>same member function interface as</i> std::exception
-};
-</pre>
- </blockquote>Exception used to indicate runtime lexical_cast
- failure.
-
-<hr>
-<!--
-The original design of lexical_cast library does not supports throwing/nonthrowing behaviour, default values,
-locales... BOOST_LEXICAL_CAST_ASSUME_C_LOCALE is a good optimization, but it breaks down the original design.
--->
<!--
- <h2><a name="BOOST_LEXICAL_CAST_ASSUME_C_LOCALE"><code>BOOST_LEXICAL_CAST_ASSUME_C_LOCALE</code></a></h2>
- <blockquote><pre>#define BOOST_LEXICAL_CAST_ASSUME_C_LOCALE</blockquote></pre>
-or,
- <blockquote><pre>g++ -DBOOST_LEXICAL_CAST_ASSUME_C_LOCALE ... (gcc on Linux/Unix)</blockquote></pre>
- <blockquote><pre>cl.exe /DBOOST_LEXICAL_CAST_ASSUME_C_LOCALE ... (Visual C++ on Windows)</blockquote></pre>
-</pre>
-Eliminate an overhead of <code>std::locale</code> if your program runs in the "C" locale. If the option is set but a program runs in other locale, <code>lexical_cast</code> result is unspecified.
-<hr>
+Copyright 2005-2007 Daniel James.
+Distributed under 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)
-->
-
-<h2><a name="faq">Frequently Asked Questions</a></h2>
-
-<table>
- <tr>
- <td valign="top"><b>Question:</b></td>
- <td>Why does <code>lexical_cast<int8_t>("127")</code> throw <code>bad_lexical_cast</code>?</td>
- </tr>
- <tr>
- <td valign="top"><b>Answer:</b></td>
- <td>The type <code>int8_t</code> is a typedef to <code>char</code> or <code>signed char</code>.
- Lexical conversion to these types is simply reading a byte from source but since the source has
- more than one byte, the exception is thrown.
- Please use other integer types such as <code>int</code> or <code>short int</code>. If bounds checking
- is important, you can also call numeric_cast:
-<pre>numeric_cast<int8_t>(lexical_cast<int>("127"));</pre>
- </td>
- </tr>
- <tr>
- <td valign="top"><b>Question:</b></td><td>What does <code>lexical_cast<std::string></code> of an <code>int8_t</code> or <code>uint8_t</code> not do what I expect?</td>
- </tr>
- <tr>
- <td valign="top"><b>Answer:</b></td><td>As above, note that <code>int8_t</code> and <code>uint8_t</code> are actually chars and are formatted as such. To avoid this, cast to an integer type first:
- <pre>lexical_cast<std::string>(static_cast<int>(n));</pre>
- </td>
- </tr>
- <tr>
- <td valign="top"><b>Question:</b></td>
- <td>The implementation always resets the <code>ios_base::skipws</code> flag of an underlying stream object. It breaks my <code>operator>></code> that works only in presence of this flag. Can you remove code that resets the flag?</td>
- </tr>
- <tr>
- <td valign="top"><b>Answer:</b></td>
- <td>May be in a future version. There is no requirement in [N1973] to reset the flag but remember that [N1973] is not yet accepted by the committee. By the way, it's a great opportunity to make your <code>operator>></code> conform to the standard. Read a good C++ book, study <code>std::sentry</code> and ios_state_saver.
- </td>
- </tr>
- <tr>
- <td valign="top"><b>Question:</b></td>
- <td>Why <code>std::cout << boost::lexical_cast<unsigned int>("-1");</code> does not throw, but outputs 4294967295?</td>
- </tr>
- <tr>
- <td valign="top"><b>Answer:</b></td>
- <td><code>boost::lexical_cast</code> has the behavior of <code>stringstream</code>, which uses <code>num_get</code> functions of <code>std::locale</code> to convert numbers. If we look at the [22.2.2.1.2] of Programming languages — C++, we'll see, that <code>num_get</code> uses the rules of <code>scanf</code> for conversions. And in the C99 standard for unsigned input value minus sign is optional, so if a negative number is read, no errors will arise and the result will be the two's complement.
- </td>
- </tr>
-</table>
-<h2><a name="references">References</a></h2>
-<ul type="square">
- <li><a name="n1973"></a>[N1973] Kevlin Henney, Beman Dawes, Lexical Conversion Library Proposal for TR2,
- N1973.
- <a name="tuning"></a><li> [Tuning] Alexander Nasonov, Fine Tuning for lexical_cast,
- Overload #74 (PDF),
- August 2006.</li>
-</ul>
-<h2><a name="changes">Changes</a></h2>
-<h3>July 2011:</h3>
-<ul type="square">
- <li>Added code to work with Inf and NaN on any platform.</li>
- <li>Better performance and less memory usage for conversions to float type (and to double type, if sizeof(double)<sizeof(long double)).</li>
-</ul>
-<h3>May 2011:</h3>
-<ul type="square">
- <li>Optimizations for "C" and other locales without number grouping.</li>
- <li>Better performance and less memory usage for unsigned char and signed char conversions.</li>
- <li>Better performance and less memory usage for conversions to arithmetic types.</li>
- <li>Better performance and less memory usage for conversions from arithmetic type to arithmetic type.</li>
- <li>Directly construct <code>Target</code> from <code>Source</code> on some conversions (like conversions from string to string, from char array to string, from char to char and others).</li>
-</ul>
-<h3>August, October 2006:</h3>
-<ul type="square">
- <li>Better performance for many combinations of <code>Source</code> and <code>Target</code>
- types. Refer to [Tuning] for more details.
- </li>
-</ul>
-<h3>June 2005:</h3>
-<ul type="square">
- <li>Call-by-const reference for the parameters. This requires partial specialization
- of class templates, so it doesn't work for MSVC 6, and it uses the original
- pass by value there.<br>
- </li>
- <li>The MSVC 6 support is deprecated, and will be removed in a future Boost
- version. </li>
-</ul>
-<h3>Earlier:</h3>
-
-<ul type="square">
- <li>The previous version of <code>lexical_cast</code> used the default stream
- precision for reading and writing floating-point numbers. For numerics that
- have a corresponding specialization of <code>std::numeric_limits</code>, the
- current version now chooses a precision to match. <br>
- <li>The previous version of <code>lexical_cast</code> did not support conversion
- to or from any wide-character-based types. For compilers with full language
- and library support for wide characters, <code>lexical_cast</code> now supports
- conversions from <code>wchar_t</code>, <code>wchar_t *</code>, and <code>std::wstring</code>
- and to <code>wchar_t</code> and <code>std::wstring</code>. <br>
- <li>The previous version of <code>lexical_cast</code> assumed that the conventional
- stream extractor operators were sufficient for reading values. However, string
- I/O is asymmetric, with the result that spaces play the role of I/O separators
- rather than string content. The current version fixes this error for <code>std::string</code>
- and, where supported, <code>std::wstring</code>: <code>lexical_cast<std::string>("Hello,
- World")</code> succeeds instead of failing with a <code>bad_lexical_cast</code>
- exception. <br>
- <li>The previous version of <code>lexical_cast</code> allowed unsafe and meaningless
- conversions to pointers. The current version now throws a <code>bad_lexical_cast</code>
- for conversions to pointers: <code>lexical_cast<char *>("Goodbye, World")</code>
- now throws an exception instead of causing undefined behavior.
-</ul>
- <p>
- <hr>
-
-<h2><a name="performance">Performance</a></h2>
-This table shows the execution time in milliseconds for 100000 calls of the following string formatters:
-
-<table border="1" width="100%">
- <tr>
-<tr><td>From->To</td><td> <code>lexical_cast</code> </td><td><code>std::stringstream</code><br>with construction</td><td><code>std::stringstream</code><br>without construction</td><td><code>sscanf</code>/<code>sprintf</code></td></tr>
- <tr><td>string->char</td><td bgcolor="#00C000"><1</td><td>91</td><td>7</td><td>10</td></tr>
- <tr><td>string->int</td><td bgcolor="#00C000">7</td><td>115</td><td>23</td><td>18</td></tr>
- <tr><td>string->unsigned int</td><td bgcolor="#00C000">7</td><td>117</td><td>22</td><td>17</td></tr>
- <tr><td>string->bool</td><td bgcolor="#00C000"><1</td><td>104</td><td>19</td><td>10</td></tr>
- <tr><td>string->float</td><td bgcolor="#00C000">13</td><td>172</td><td>60</td><td>33</td></tr>
- <tr><td>char->string</td><td bgcolor="#00C000">7</td><td>105</td><td>16</td><td>12</td></tr>
- <tr><td>int->string</td><td bgcolor="#00C000">15</td><td>131</td><td>21</td><td>17</td></tr>
- <tr><td>unsigned int->string</td><td bgcolor="#00C000">14</td><td>125</td><td>21</td><td>17</td></tr>
- <tr><td>bool->string</td><td bgcolor="#00C000">7</td><td>122</td><td>24</td><td>12</td></tr>
- <tr><td>float->string</td><td>124</td><td>223</td><td>115</td><td bgcolor="#00C000">48</td></tr>
- <tr><td>char*->string</td><td bgcolor="#00C000">9</td><td>123</td><td>20</td><td>---</td></tr>
- <tr><td>int->int</td><td bgcolor="#00C000"><1</td><td>120</td><td>26</td><td>---</td></tr>
- <tr><td>float->float</td><td bgcolor="#00C000"><1</td><td>262</td><td>142</td><td>---</td></tr>
-</table>
-
-Fastest results are highlitened with green.
- <hr>
-<div align="right"><small><i>Copyright © Kevlin Henney, 2000-2005</i></small></div>
-<div align="right"><small><i>Copyright © Alexander Nasonov, 2006-2010</i></small></div>
-<div align="right"><small><i>Copyright © Antony Polukhin, 2011</i></small></div>
-<div align="right"><small><i>
- Distributed under 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)</i></small>
-</div>
- </body>
+<html>
+<head>
+ <meta http-equiv="refresh" content="0; URL=../../doc/html/boost_lexical_cast.html">
+</head>
+<body>
+Automatic redirection failed, please go to
+../../doc/html/boost_lexical_cast.html
+</body>
</html>
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