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[SVN r8702]
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Dave Abrahams
323
numeric_traits_test.cpp
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323
numeric_traits_test.cpp
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// (C) Copyright David Abrahams 2001. Permission to copy, use, modify,
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// sell and distribute this software is granted provided this
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// copyright notice appears in all copies. This software is provided
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// "as is" without express or implied warranty, and with no claim as
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// to its suitability for any purpose.
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// See http://www.boost.org for most recent version including documentation.
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// Revision History
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// 21 Jan 2001 Initial version (David Abrahams)
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#include <boost/detail/numeric_traits.hpp>
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#include <cassert>
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#include <boost/type_traits.hpp>
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#include <boost/static_assert.hpp>
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#include <boost/cstdint.hpp>
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#include <boost/utility.hpp>
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#include <boost/lexical_cast.hpp>
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#include <climits>
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#include <typeinfo>
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#include <iostream>
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#include <string>
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#ifndef BOOST_NO_LIMITS
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# include <limits>
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#endif
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// A macro for declaring class compile-time constants.
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#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
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# define DECLARE_CLASS_CONST(type, init) static const type init
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#else
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# define DECLARE_CLASS_CONST(type, init) enum { init }
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#endif
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// template class complement_traits<Number> --
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//
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// statically computes the max and min for 1s and 2s-complement binary
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// numbers. This helps on platforms without <limits> support. It also shows
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// an example of a recursive template that works with MSVC!
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//
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template <unsigned size> struct complement; // forward
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// The template complement, below, does all the real work, using "poor man's
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// partial specialization". We need complement_traits_aux<> so that MSVC doesn't
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// complain about undefined min/max as we're trying to recursively define them.
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template <class Number, unsigned size>
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struct complement_traits_aux
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{
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DECLARE_CLASS_CONST(Number, max = complement<size>::template traits<Number>::max);
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DECLARE_CLASS_CONST(Number, min = complement<size>::template traits<Number>::min);
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};
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template <unsigned size>
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struct complement
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{
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template <class Number>
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struct traits
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{
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private:
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// indirection through complement_traits_aux neccessary to keep MSVC happy
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typedef complement_traits_aux<Number, size - 1> prev;
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public:
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DECLARE_CLASS_CONST(Number, max =
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Number(Number(prev::max) << CHAR_BIT)
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+ Number(UCHAR_MAX));
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DECLARE_CLASS_CONST(Number, min = Number(Number(prev::min) << CHAR_BIT));
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};
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};
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// Template class complement_base<> -- defines values for min and max for
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// complement<1>, at the deepest level of recursion. Uses "poor man's partial
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// specialization" again.
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template <bool is_signed> struct complement_base;
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template <> struct complement_base<false>
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{
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template <class Number>
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struct values
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{
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DECLARE_CLASS_CONST(Number, min = 0);
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DECLARE_CLASS_CONST(Number, max = UCHAR_MAX);
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};
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};
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template <> struct complement_base<true>
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{
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template <class Number>
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struct values
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{
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DECLARE_CLASS_CONST(Number, min = SCHAR_MIN);
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DECLARE_CLASS_CONST(Number, max = SCHAR_MAX);
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};
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};
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// Base specialization of complement, puts an end to the recursion.
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template <>
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struct complement<1>
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{
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template <class Number>
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struct traits
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{
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DECLARE_CLASS_CONST(bool, is_signed = boost::detail::is_signed<Number>::value);
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DECLARE_CLASS_CONST(Number, min =
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complement_base<is_signed>::template values<Number>::min);
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DECLARE_CLASS_CONST(Number, max =
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complement_base<is_signed>::template values<Number>::max);
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};
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};
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// Now here's the "pretty" template you're intended to actually use.
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// complement_traits<Number>::min, complement_traits<Number>::max are the
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// minimum and maximum values of Number if Number is a built-in integer type.
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template <class Number>
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struct complement_traits
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{
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DECLARE_CLASS_CONST(Number, max = (complement_traits_aux<Number, sizeof(Number)>::max));
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DECLARE_CLASS_CONST(Number, min = (complement_traits_aux<Number, sizeof(Number)>::min));
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};
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// Support for streaming various numeric types in exactly the format I want. I
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// needed this in addition to all the assertions so that I could see exactly
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// what was going on.
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//
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// Numbers go through a 2-stage conversion process (by default, though, no real
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// conversion).
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//
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template <class T> struct stream_as {
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typedef T t1;
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typedef T t2;
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};
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// char types first get converted to unsigned char, then to unsigned.
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template <> struct stream_as<char> {
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typedef unsigned char t1;
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typedef unsigned t2;
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};
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template <> struct stream_as<unsigned char> {
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typedef unsigned char t1; typedef unsigned t2;
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};
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template <> struct stream_as<signed char> {
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typedef unsigned char t1; typedef unsigned t2;
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};
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#if defined(BOOST_MSVC) // No intmax streaming built-in
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// On this platform, __int64 and __uint64 get streamed as strings
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template <> struct stream_as<boost::uintmax_t> {
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typedef std::string t1;
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typedef std::string t2;
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};
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template <> struct stream_as<boost::intmax_t> {
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typedef std::string t1;
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typedef std::string t2;
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};
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#endif
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// Standard promotion process for streaming
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template <class T> struct promote
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{
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typename stream_as<T>::t1 static from(T x) {
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typedef typename stream_as<T>::t1 t1;
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return t1(x);
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}
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};
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#if defined(BOOST_MSVC) // No intmax streaming built-in
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// On this platform, stream them as long/unsigned long if they fit.
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// Otherwise, write a string.
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template <> struct promote<boost::uintmax_t> {
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std::string static from(const boost::uintmax_t x) {
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if (x > ULONG_MAX)
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return std::string("large unsigned value");
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else
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return boost::lexical_cast<std::string>((unsigned long)x);
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}
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};
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template <> struct promote<boost::intmax_t> {
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std::string static from(const boost::intmax_t x) {
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if (x > boost::intmax_t(ULONG_MAX))
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return std::string("large positive signed value");
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else if (x >= 0)
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return boost::lexical_cast<std::string>((unsigned long)x);
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if (x < boost::intmax_t(LONG_MIN))
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return std::string("large negative signed value");
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else
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return boost::lexical_cast<std::string>((long)x);
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}
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};
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#endif
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// This is the function which converts types to the form I want to stream them in.
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template <class T>
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typename stream_as<T>::t2 stream_number(T x)
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{
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return promote<T>::from(x);
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}
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//
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// Tests for built-in signed and unsigned types
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//
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// Tag types for selecting tests
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struct unsigned_tag {};
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struct signed_tag {};
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// Tests for unsigned numbers. The extra default Number parameter works around
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// an MSVC bug.
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template <class Number>
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void test_aux(unsigned_tag, Number* = 0)
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{
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typedef typename boost::detail::numeric_traits<Number>::difference_type difference_type;
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BOOST_STATIC_ASSERT(!boost::detail::is_signed<Number>::value);
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BOOST_STATIC_ASSERT(
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(sizeof(Number) < sizeof(boost::intmax_t))
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| (boost::is_same<difference_type, boost::intmax_t>::value));
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// Force casting to Number here to work around the fact that it's an enum on MSVC
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BOOST_STATIC_ASSERT(Number(complement_traits<Number>::max) > Number(0));
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BOOST_STATIC_ASSERT(Number(complement_traits<Number>::min) == Number(0));
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const Number max = complement_traits<Number>::max;
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const Number min = complement_traits<Number>::min;
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const Number test_max = (sizeof(Number) < sizeof(boost::intmax_t))
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? max
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: max / 2 - 1;
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std::cout << std::hex << "(unsigned) min = " << stream_number(min) << ", max = "
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<< stream_number(max) << "..." << std::flush;
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std::cout << "difference_type = " << typeid(difference_type).name() << "..."
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<< std::flush;
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difference_type d1 = boost::detail::numeric_distance(Number(0), test_max);
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difference_type d2 = boost::detail::numeric_distance(test_max, Number(0));
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std::cout << "0->" << stream_number(test_max) << "==" << std::dec << stream_number(d1) << "; "
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<< std::hex << stream_number(test_max) << "->0==" << std::dec << stream_number(d2) << "..." << std::flush;
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assert(d1 == difference_type(test_max));
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assert(d2 == -difference_type(test_max));
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}
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// Tests for signed numbers. The extra default Number parameter works around an
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// MSVC bug.
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template <class Number>
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void test_aux(signed_tag, Number* = 0)
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{
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typedef typename boost::detail::numeric_traits<Number>::difference_type difference_type;
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BOOST_STATIC_ASSERT(boost::detail::is_signed<Number>::value);
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BOOST_STATIC_ASSERT(
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(sizeof(Number) < sizeof(boost::intmax_t))
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| (boost::is_same<difference_type, Number>::value));
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// Force casting to Number here to work around the fact that it's an enum on MSVC
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BOOST_STATIC_ASSERT(Number(complement_traits<Number>::max) > Number(0));
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BOOST_STATIC_ASSERT(Number(complement_traits<Number>::min) < Number(0));
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const Number max = complement_traits<Number>::max;
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const Number min = complement_traits<Number>::min;
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std::cout << std::hex << "min = " << stream_number(min) << ", max = "
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<< stream_number(max) << "..." << std::flush;
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std::cout << "difference_type = " << typeid(difference_type).name() << "..."
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<< std::flush;
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assert(min < max);
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difference_type d1 = boost::detail::numeric_distance(min, max);
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difference_type d2 = boost::detail::numeric_distance(max, min);
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if (sizeof(Number) < sizeof(boost::intmax_t))
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{
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std::cout << stream_number(min) << "->" << stream_number(max) << "==";
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std::cout << std::dec << stream_number(d1) << "; ";
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std::cout << std::hex << stream_number(max) << "->" << stream_number(min)
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<< "==" << std::dec << stream_number(d2) << "..." << std::flush;
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assert(d1 == difference_type(max) - difference_type(min));
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assert(d2 == difference_type(min) - difference_type(max));
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}
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}
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// Test for all numbers. The extra default Number parameter works around an MSVC
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// bug.
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template <class Number>
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void test(Number* = 0)
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{
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std::cout << "testing " << typeid(Number).name() << "..." << std::flush;
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typedef typename boost::detail::numeric_traits<Number>::difference_type difference_type;
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BOOST_STATIC_ASSERT(boost::detail::is_signed<difference_type>::value);
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typedef typename boost::detail::if_true<
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boost::detail::is_signed<Number>::value
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>::template then<signed_tag, unsigned_tag>::type signedness;
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test_aux<Number>(signedness());
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std::cout << "passed" << std::endl;
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}
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int main()
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{
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test<char>();
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test<unsigned char>();
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test<signed char>();
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test<short>();
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test<unsigned short>();
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test<int>();
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test<unsigned int>();
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test<long>();
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test<unsigned long>();
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#if defined(ULLONG_MAX) || defined(ULONG_LONG_MAX)
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test<long long>();
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test<unsigned long long>();
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#elif defined(BOOST_MSVC)
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// The problem of not having compile-time static class constants other than
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// enums prevents this from working, since values get truncated.
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// test<boost::uintmax_t>();
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// test<boost::intmax_t>();
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#endif
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return 0;
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}
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