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Old numeric_cast<> completely replaced by new code (except that the old code is retained as a fallback mechanism for old broken compilers that can't deal with the new code)

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[SVN r29761]
This commit is contained in:
Fernando Cacciola
2005-06-23 23:33:01 +00:00
parent e331fc2a21
commit e66d58e6de
4 changed files with 28 additions and 374 deletions
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98
cast.htm
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@@ -3,7 +3,7 @@
<html> <html>
<head> <head>
<meta name="generator" content= <meta name="generator" content=
"HTML Tidy for Cygwin (vers 1st April 2002), see www.w3.org"> "Microsoft FrontPage 5.0">
<meta http-equiv="Content-Type" content= <meta http-equiv="Content-Type" content=
"text/html; charset=windows-1252"> "text/html; charset=windows-1252">
<meta name="GENERATOR" content="Microsoft FrontPage 4.0"> <meta name="GENERATOR" content="Microsoft FrontPage 4.0">
@@ -19,10 +19,9 @@
<h2><a name="Cast Functions">Cast Functions</a></h2> <h2><a name="Cast Functions">Cast Functions</a></h2>
<p>The header <a href="../../boost/cast.hpp">boost/cast.hpp</a> provides <p>The header <a href="../../boost/cast.hpp">boost/cast.hpp</a> provides <code>
<a href="#Polymorphic_cast"><code>polymorphic_cast</code></a>, <a href= <a href="#Polymorphic_cast">polymorphic_cast</a> and</code> <a href=
"#Polymorphic_cast"><code>polymorphic_downcast</code></a>, and <a href= "#Polymorphic_cast"><code>polymorphic_downcast</code></a> function templates designed to
"#numeric_cast"><code>numeric_cast</code></a> function templates designed to
complement the C++ built-in casts.</p> complement the C++ built-in casts.</p>
<p>The program <a href="cast_test.cpp">cast_test.cpp</a> can be used to <p>The program <a href="cast_test.cpp">cast_test.cpp</a> can be used to
@@ -62,9 +61,8 @@
<p>A <code>polymorphic_downcast</code> should be used for <p>A <code>polymorphic_downcast</code> should be used for
downcasts that you are certain should succeed. Error checking is downcasts that you are certain should succeed. Error checking is
only performed in translation units where <code>NDEBUG</code> is only performed in translation units where <code>NDEBUG</code> is
not defined, via not defined, via
<pre> <pre> assert( dynamic_cast&lt;Derived&gt;(x) == x )
assert( dynamic_cast&lt;Derived&gt;(x) == x )
</pre> where <code>x</code> is the source pointer. This approach </pre> where <code>x</code> is the source pointer. This approach
ensures that not only is a non-zero pointer returned, but also ensures that not only is a non-zero pointer returned, but also
that it is correct in the presence of multiple inheritance. that it is correct in the presence of multiple inheritance.
@@ -86,8 +84,7 @@
<h3>polymorphic_cast and polymorphic_downcast synopsis</h3> <h3>polymorphic_cast and polymorphic_downcast synopsis</h3>
<blockquote> <blockquote>
<pre> <pre>namespace boost {
namespace boost {
template &lt;class Derived, class Base&gt; template &lt;class Derived, class Base&gt;
inline Derived polymorphic_cast(Base* x); inline Derived polymorphic_cast(Base* x);
@@ -106,8 +103,7 @@ inline Derived polymorphic_downcast(Base* x);
<h3>polymorphic_downcast example</h3> <h3>polymorphic_downcast example</h3>
<blockquote> <blockquote>
<pre> <pre>#include &lt;boost/cast.hpp&gt;
#include &lt;boost/cast.hpp&gt;
... ...
class Fruit { public: virtual ~Fruit(){}; ... }; class Fruit { public: virtual ~Fruit(){}; ... };
class Banana : public Fruit { ... }; class Banana : public Fruit { ... };
@@ -119,85 +115,20 @@ void f( Fruit * fruit ) {
</pre> </pre>
</blockquote> </blockquote>
<h3><a name="numeric_cast">numeric_cast</a></h3>
<p>A <code>static_cast</code> or implicit conversion will not detect failure to
preserve range for numeric casts. The <code>numeric_cast</code> function
templates are similar to <code>static_cast</code> and certain (dubious)
implicit conversions in this respect, except that they detect loss of
numeric range. An exception is thrown when a runtime value-preservation
check fails.</p>
<p>The requirements on the argument and result types are:</p>
<blockquote>
<ul>
<li>Both argument and result types are CopyConstructible [ISO Std
20.1.3].</li>
<li>Both argument and result types are Numeric, defined by
<code>std::numeric_limits&lt;&gt;::is_specialized</code> being
true.</li>
<li>The argument can be converted to the result type using
<code>static_cast</code>.</li>
</ul>
</blockquote>
<h3>numeric_cast synopsis</h3>
<blockquote>
<pre>
namespace boost {
class bad_numeric_cast : public std::bad_cast {...};
template&lt;typename Target, typename Source&gt;
inline Target numeric_cast(Source arg);
// Throws: bad_numeric_cast unless, in converting arg from Source to Target,
// there is no loss of negative range, and no underflow, and no
// overflow, as determined by std::numeric_limits
// Returns: static_cast&lt;Target&gt;(arg)
}
</pre>
</blockquote>
<h3>numeric_cast example</h3>
<blockquote>
<pre>
#include &lt;boost/cast.hpp&gt;
using namespace boost::cast;
void ariane(double vx)
{
...
unsigned short dx = numeric_cast&lt;unsigned short&gt;(vx);
...
}
</pre>
</blockquote>
<h3>numeric_cast rationale</h3>
<p>The form of the throws condition is specified so that != is not a
required operation.</p>
<h3>History</h3> <h3>History</h3>
<p><code>polymorphic_cast</code> was suggested by Bjarne Stroustrup in "The C++ <p><code>polymorphic_cast</code> was suggested by Bjarne Stroustrup in "The C++
Programming Language".<br> Programming Language".<br>
<code>polymorphic_downcast</code> was contributed by <a href= <code>polymorphic_downcast</code> was contributed by <a href=
"../../people/dave_abrahams.htm">Dave Abrahams</a>.<code><br> "../../people/dave_abrahams.htm">Dave Abrahams</a>.<code><br>
numeric_cast</code> was contributed by <a href= An old
"../../people/kevlin_henney.htm">Kevlin Henney</a>.</p> numeric_cast</code> that was contributed by <a href=
"../../people/kevlin_henney.htm">Kevlin Henney</a> is now superseeded by the <a href="../numeric/conversion/doc/index.html">Boost Numeric Conversion Library</a></p>
<hr> <hr>
<p>Revised <p>Revised
<!--webbot bot="Timestamp" s-type="EDITED" s-format="%d %B, %Y" startspan <!--webbot bot="Timestamp" s-type="EDITED" s-format="%d %B, %Y" startspan
-->06 January, 2001 -->June 23, 2005<!--webbot bot="Timestamp" endspan i-checksum="30348"
<!--webbot bot="Timestamp" endspan i-checksum="38320"
--></p> --></p>
<p>&copy; Copyright boost.org 1999. Permission to copy, use, modify, sell <p>&copy; Copyright boost.org 1999. Permission to copy, use, modify, sell
@@ -206,5 +137,4 @@ void ariane(double vx)
or implied warranty, and with no claim as to its suitability for any or implied warranty, and with no claim as to its suitability for any
purpose.</p> purpose.</p>
</body> </body>
</html> </html>

294
include/boost/cast.hpp
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@@ -1,6 +1,6 @@
// boost cast.hpp header file ----------------------------------------------// // boost cast.hpp header file ----------------------------------------------//
// (C) Copyright Kevlin Henney and Dave Abrahams 1999. // (C) Copyright Kevlin Henney and Dave Abrahams 1999.
// Distributed under the Boost // Distributed under the Boost
// Software License, Version 1.0. (See accompanying file // Software License, Version 1.0. (See accompanying file
// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -8,9 +8,10 @@
// See http://www.boost.org/libs/conversion for Documentation. // See http://www.boost.org/libs/conversion for Documentation.
// Revision History // Revision History
// 02 Apr 01 Removed BOOST_NO_LIMITS workarounds and included // 23 JUn 05 numeric_cast removed and redirected to the new verion (Fernando Cacciola)
// <boost/limits.hpp> instead (the workaround did not // 02 Apr 01 Removed BOOST_NO_LIMITS workarounds and included
// actually compile when BOOST_NO_LIMITS was defined in // <boost/limits.hpp> instead (the workaround did not
// actually compile when BOOST_NO_LIMITS was defined in
// any case, so we loose nothing). (John Maddock) // any case, so we loose nothing). (John Maddock)
// 21 Jan 01 Undid a bug I introduced yesterday. numeric_cast<> never // 21 Jan 01 Undid a bug I introduced yesterday. numeric_cast<> never
// worked with stock GCC; trying to get it to do that broke // worked with stock GCC; trying to get it to do that broke
@@ -26,14 +27,14 @@
// (Dave Abrahams) // (Dave Abrahams)
// 30 Jun 00 More MSVC6 wordarounds. See comments below. (Dave Abrahams) // 30 Jun 00 More MSVC6 wordarounds. See comments below. (Dave Abrahams)
// 28 Jun 00 Removed implicit_cast<>. See comment below. (Beman Dawes) // 28 Jun 00 Removed implicit_cast<>. See comment below. (Beman Dawes)
// 27 Jun 00 More MSVC6 workarounds // 27 Jun 00 More MSVC6 workarounds
// 15 Jun 00 Add workarounds for MSVC6 // 15 Jun 00 Add workarounds for MSVC6
// 2 Feb 00 Remove bad_numeric_cast ";" syntax error (Doncho Angelov) // 2 Feb 00 Remove bad_numeric_cast ";" syntax error (Doncho Angelov)
// 26 Jan 00 Add missing throw() to bad_numeric_cast::what(0 (Adam Levar) // 26 Jan 00 Add missing throw() to bad_numeric_cast::what(0 (Adam Levar)
// 29 Dec 99 Change using declarations so usages in other namespaces work // 29 Dec 99 Change using declarations so usages in other namespaces work
// correctly (Dave Abrahams) // correctly (Dave Abrahams)
// 23 Sep 99 Change polymorphic_downcast assert to also detect M.I. errors // 23 Sep 99 Change polymorphic_downcast assert to also detect M.I. errors
// as suggested Darin Adler and improved by Valentin Bonnard. // as suggested Darin Adler and improved by Valentin Bonnard.
// 2 Sep 99 Remove controversial asserts, simplify, rename. // 2 Sep 99 Remove controversial asserts, simplify, rename.
// 30 Aug 99 Move to cast.hpp, replace value_cast with numeric_cast, // 30 Aug 99 Move to cast.hpp, replace value_cast with numeric_cast,
// place in nested namespace. // place in nested namespace.
@@ -68,7 +69,7 @@ namespace boost
// polymorphic_cast --------------------------------------------------------// // polymorphic_cast --------------------------------------------------------//
// Runtime checked polymorphic downcasts and crosscasts. // Runtime checked polymorphic downcasts and crosscasts.
// Suggested in The C++ Programming Language, 3rd Ed, Bjarne Stroustrup, // Suggested in The C++ Programming Language, 3rd Ed, Bjarne Stroustrup,
// section 15.8 exercise 1, page 425. // section 15.8 exercise 1, page 425.
template <class Target, class Source> template <class Target, class Source>
@@ -98,284 +99,9 @@ namespace boost
// implicit_cast -----------------------------------------------------------// // implicit_cast -----------------------------------------------------------//
// //
// Removed due to uncertain purpose. Use either numeric_cast (see below) // Removed due to uncertain purpose. Use either numeric_cast (see below)
// or static_cast according to the need. // or static_cast according to the need.
// numeric_cast and related exception --------------------------------------// #include <boost/numeric/conversion/cast.hpp>
// Contributed by Kevlin Henney
// bad_numeric_cast --------------------------------------------------------//
// exception used to indicate runtime numeric_cast failure
class bad_numeric_cast : public std::bad_cast
{
public:
// constructors, destructors and assignment operator defaulted
// function inlined for brevity and consistency with rest of library
virtual const char *what() const throw()
{
return "bad numeric cast: loss of range in numeric_cast";
}
};
// numeric_cast ------------------------------------------------------------//
#if !defined(BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS) || defined(BOOST_SGI_CPP_LIMITS)
namespace detail
{
template <class T>
struct signed_numeric_limits : std::numeric_limits<T>
{
static inline T min BOOST_PREVENT_MACRO_SUBSTITUTION ()
{
return (std::numeric_limits<T>::min)() >= 0
// unary minus causes integral promotion, thus the static_cast<>
? static_cast<T>(-(std::numeric_limits<T>::max)())
: (std::numeric_limits<T>::min)();
};
};
// Move to namespace boost in utility.hpp?
template <class T, bool specialized>
struct fixed_numeric_limits_base
: public if_true< std::numeric_limits<T>::is_signed >
::BOOST_NESTED_TEMPLATE then< signed_numeric_limits<T>,
std::numeric_limits<T>
>::type
{};
template <class T>
struct fixed_numeric_limits
: fixed_numeric_limits_base<T,(std::numeric_limits<T>::is_specialized)>
{};
# ifdef BOOST_HAS_LONG_LONG
// cover implementations which supply no specialization for long
// long / unsigned long long. Not intended to be full
// numeric_limits replacements, but good enough for numeric_cast<>
template <>
struct fixed_numeric_limits_base< ::boost::long_long_type, false>
{
BOOST_STATIC_CONSTANT(bool, is_specialized = true);
BOOST_STATIC_CONSTANT(bool, is_signed = true);
static ::boost::long_long_type max BOOST_PREVENT_MACRO_SUBSTITUTION ()
{
# ifdef LONGLONG_MAX
return LONGLONG_MAX;
# else
return 9223372036854775807LL; // hope this is portable
# endif
}
static ::boost::long_long_type min BOOST_PREVENT_MACRO_SUBSTITUTION ()
{
# ifdef LONGLONG_MIN
return LONGLONG_MIN;
# else
return -( 9223372036854775807LL )-1; // hope this is portable
# endif
}
};
template <>
struct fixed_numeric_limits_base< ::boost::ulong_long_type, false>
{
BOOST_STATIC_CONSTANT(bool, is_specialized = true);
BOOST_STATIC_CONSTANT(bool, is_signed = false);
static ::boost::ulong_long_type max BOOST_PREVENT_MACRO_SUBSTITUTION ()
{
# ifdef ULONGLONG_MAX
return ULONGLONG_MAX;
# else
return 0xffffffffffffffffULL; // hope this is portable
# endif
}
static ::boost::ulong_long_type min BOOST_PREVENT_MACRO_SUBSTITUTION () { return 0; }
};
# endif
} // namespace detail
// less_than_type_min -
// x_is_signed should be numeric_limits<X>::is_signed
// y_is_signed should be numeric_limits<Y>::is_signed
// y_min should be numeric_limits<Y>::min()
//
// check(x, y_min) returns true iff x < y_min without invoking comparisons
// between signed and unsigned values.
//
// "poor man's partial specialization" is in use here.
template <bool x_is_signed, bool y_is_signed>
struct less_than_type_min
{
template <class X, class Y>
static bool check(X x, Y y_min)
{ return x < y_min; }
};
template <>
struct less_than_type_min<false, true>
{
template <class X, class Y>
static bool check(X, Y)
{ return false; }
};
template <>
struct less_than_type_min<true, false>
{
template <class X, class Y>
static bool check(X x, Y)
{ return x < 0; }
};
// greater_than_type_max -
// same_sign should be:
// numeric_limits<X>::is_signed == numeric_limits<Y>::is_signed
// y_max should be numeric_limits<Y>::max()
//
// check(x, y_max) returns true iff x > y_max without invoking comparisons
// between signed and unsigned values.
//
// "poor man's partial specialization" is in use here.
template <bool same_sign, bool x_is_signed>
struct greater_than_type_max;
template<>
struct greater_than_type_max<true, true>
{
template <class X, class Y>
static inline bool check(X x, Y y_max)
{ return x > y_max; }
};
template <>
struct greater_than_type_max<false, true>
{
// What does the standard say about this? I think it's right, and it
// will work with every compiler I know of.
template <class X, class Y>
static inline bool check(X x, Y)
{ return x >= 0 && static_cast<X>(static_cast<Y>(x)) != x; }
# if defined(BOOST_MSVC) && BOOST_MSVC <= 1200
// MSVC6 can't static_cast unsigned __int64 -> floating types
# define BOOST_UINT64_CAST(src_type) \
static inline bool check(src_type x, unsigned __int64) \
{ \
if (x < 0) return false; \
unsigned __int64 y = static_cast<unsigned __int64>(x); \
bool odd = y & 0x1; \
__int64 div2 = static_cast<__int64>(y >> 1); \
return ((static_cast<src_type>(div2) * 2.0) + odd) != x; \
}
BOOST_UINT64_CAST(long double);
BOOST_UINT64_CAST(double);
BOOST_UINT64_CAST(float);
# undef BOOST_UINT64_CAST
# endif
};
template<>
struct greater_than_type_max<true, false>
{
template <class X, class Y>
static inline bool check(X x, Y y_max)
{ return x > y_max; }
};
template <>
struct greater_than_type_max<false, false>
{
// What does the standard say about this? I think it's right, and it
// will work with every compiler I know of.
template <class X, class Y>
static inline bool check(X x, Y)
{ return static_cast<X>(static_cast<Y>(x)) != x; }
};
#else // use #pragma hacks if available
namespace detail
{
# if BOOST_MSVC
# pragma warning(push)
# pragma warning(disable : 4018)
# pragma warning(disable : 4146)
#elif defined(__BORLANDC__)
# pragma option push -w-8041
# endif
// Move to namespace boost in utility.hpp?
template <class T>
struct fixed_numeric_limits : public std::numeric_limits<T>
{
static inline T min BOOST_PREVENT_MACRO_SUBSTITUTION ()
{
return std::numeric_limits<T>::is_signed && (std::numeric_limits<T>::min)() >= 0
? T(-(std::numeric_limits<T>::max)()) : (std::numeric_limits<T>::min)();
}
};
# if BOOST_MSVC
# pragma warning(pop)
#elif defined(__BORLANDC__)
# pragma option pop
# endif
} // namespace detail
#endif
template<typename Target, typename Source>
inline Target numeric_cast(Source arg BOOST_EXPLICIT_DEFAULT_TARGET)
{
// typedefs abbreviating respective trait classes
typedef detail::fixed_numeric_limits<Source> arg_traits;
typedef detail::fixed_numeric_limits<Target> result_traits;
#if defined(BOOST_STRICT_CONFIG) \
|| (!defined(__HP_aCC) || __HP_aCC > 33900) \
&& (!defined(BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS) \
|| defined(BOOST_SGI_CPP_LIMITS))
// typedefs that act as compile time assertions
// (to be replaced by boost compile time assertions
// as and when they become available and are stable)
typedef bool argument_must_be_numeric[arg_traits::is_specialized];
typedef bool result_must_be_numeric[result_traits::is_specialized];
const bool arg_is_signed = arg_traits::is_signed;
const bool result_is_signed = result_traits::is_signed;
const bool same_sign = arg_is_signed == result_is_signed;
if (less_than_type_min<arg_is_signed, result_is_signed>::check(arg, (result_traits::min)())
|| greater_than_type_max<same_sign, arg_is_signed>::check(arg, (result_traits::max)())
)
#else // We need to use #pragma hacks if available
# if BOOST_MSVC
# pragma warning(push)
# pragma warning(disable : 4018)
#elif defined(__BORLANDC__)
#pragma option push -w-8012
# endif
if ((arg < 0 && !result_traits::is_signed) // loss of negative range
|| (arg_traits::is_signed && arg < (result_traits::min)()) // underflow
|| arg > (result_traits::max)()) // overflow
# if BOOST_MSVC
# pragma warning(pop)
#elif defined(__BORLANDC__)
#pragma option pop
# endif
#endif
{
throw bad_numeric_cast();
}
return static_cast<Target>(arg);
} // numeric_cast
# undef BOOST_EXPLICIT_DEFAULT_TARGET # undef BOOST_EXPLICIT_DEFAULT_TARGET

9
index.html
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@@ -3,7 +3,7 @@
<head> <head>
<meta http-equiv="Content-Language" content="en-us"> <meta http-equiv="Content-Language" content="en-us">
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252"> <meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<meta name="GENERATOR" content="Microsoft FrontPage 4.0"> <meta name="GENERATOR" content="Microsoft FrontPage 5.0">
<meta name="ProgId" content="FrontPage.Editor.Document"> <meta name="ProgId" content="FrontPage.Editor.Document">
<title>Boost Conversion Library</title> <title>Boost Conversion Library</title>
</head> </head>
@@ -22,8 +22,7 @@ supplied by several headers:</p>
<ul> <ul>
<li>The <a href="cast.htm">boost/cast</a> header provides <b>polymorphic_cast&lt;&gt;</b> <li>The <a href="cast.htm">boost/cast</a> header provides <b>polymorphic_cast&lt;&gt;</b>
and <b>polymorphic_downcast&lt;&gt;</b> to perform safe casting between and <b>polymorphic_downcast&lt;&gt;</b> to perform safe casting between
polymorphic types, and <b> numeric_cast</b><i>&lt;&gt;</i> to perform safe casting polymorphic types.<br>
between numeric types.<br>
</li> </li>
<li>The <a href="lexical_cast.htm">boost/lexical_cast</a> header provides <b>lexical_cast&lt;&gt;</b> <li>The <a href="lexical_cast.htm">boost/lexical_cast</a> header provides <b>lexical_cast&lt;&gt;</b>
general literal text conversions, such as an <code>int</code> represented as general literal text conversions, such as an <code>int</code> represented as
@@ -31,9 +30,9 @@ supplied by several headers:</p>
</ul> </ul>
<hr> <hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" <p>Revised <!--webbot bot="Timestamp" S-Type="EDITED"
S-Format="%d %B, %Y" startspan -->06 January, 2001<!--webbot bot="Timestamp" endspan i-checksum="38320" --> S-Format="%d %B, %Y" startspan -->June 23, 2005<!--webbot bot="Timestamp" endspan i-checksum="30348" -->
</p> </p>
</body> </body>
</html> </html>

1
test/Jamfile
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@@ -27,7 +27,6 @@ DEPENDS all : test ;
: [ run implicit_cast.cpp ] : [ run implicit_cast.cpp ]
[ compile-fail implicit_cast_fail.cpp ] [ compile-fail implicit_cast_fail.cpp ]
[ run ../cast_test.cpp ] [ run ../cast_test.cpp ]
[ run ../numeric_cast_test.cpp ]
[ run ../lexical_cast_test.cpp ] [ run ../lexical_cast_test.cpp ]
; ;
} }