// Boost.Units - A C++ library for zero-overhead dimensional analysis and
// unit/quantity manipulation and conversion
//
// Copyright (C) 2003-2008 Matthias Christian Schabel
// Copyright (C) 2007-2008 Steven Watanabe
//
// 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)
#ifndef BOOST_UNITS_CONVERSION_HPP
#define BOOST_UNITS_CONVERSION_HPP
/// \file
/// \brief Template for defining conversions between quantities.
#include
namespace boost {
namespace units {
template
struct conversion_helper;
#ifdef BOOST_UNITS_DOXYGEN
/// Template for defining conversions between
/// quantities. This template should be specialized
/// for every quantity that allows conversions.
/// For example, if you have a two units
/// called pair and dozen you would write
/// @code
/// namespace boost {
/// namespace units {
/// template
/// struct conversion_helper, quantity >
/// {
/// static quantity convert(const quantity& source)
/// {
/// return(quantity::from_value(6 * source.value()));
/// }
/// };
/// }
/// }
/// @endcode
///
/// In most cases, the predefined specializations for @c unit
/// and @c absolute should be sufficient, so users should rarely
/// need to use this.
template
struct conversion_helper
{
static BOOST_CONSTEXPR To convert(const From&);
};
#endif
/// Defines the conversion factor from a base unit to any unit
/// or to another base unit with the correct dimensions. Uses
/// of this macro must appear at global scope.
/// If the destination unit is a base unit or a unit that contains
/// only one base unit which is raised to the first power (e.g. feet->meters)
/// the reverse (meters->feet in this example) need not be defined explicitly.
#define BOOST_UNITS_DEFINE_CONVERSION_FACTOR(Source, Destination, type_, value_) \
namespace boost { \
namespace units { \
template<> \
struct select_base_unit_converter< \
unscale::type, \
unscale::type>::type \
> \
{ \
typedef Source source_type; \
typedef reduce_unit::type destination_type; \
}; \
template<> \
struct base_unit_converter::type> \
{ \
BOOST_STATIC_CONSTEXPR bool is_defined = true; \
typedef type_ type; \
static BOOST_CONSTEXPR type value() { return(value_); } \
}; \
} \
} \
void boost_units_require_semicolon()
/// Defines the conversion factor from a base unit to any other base
/// unit with the same dimensions. Params should be a Boost.Preprocessor
/// Seq of template parameters, such as (class T1)(class T2)
/// All uses of must appear at global scope. The reverse conversion will
/// be defined automatically. This macro is a little dangerous, because,
/// unlike the non-template form, it will silently fail if either base
/// unit is scaled. This is probably not an issue if both the source
/// and destination types depend on the template parameters, but be aware
/// that a generic conversion to kilograms is not going to work.
#define BOOST_UNITS_DEFINE_CONVERSION_FACTOR_TEMPLATE(Params, Source, Destination, type_, value_) \
namespace boost { \
namespace units { \
template \
struct base_unit_converter< \
Source, \
BOOST_UNITS_MAKE_HETEROGENEOUS_UNIT(Destination, typename Source::dimension_type)\
> \
{ \
BOOST_STATIC_CONSTEXPR bool is_defined = true; \
typedef type_ type; \
static BOOST_CONSTEXPR type value() { return(value_); } \
}; \
} \
} \
void boost_units_require_semicolon()
/// Specifies the default conversion to be applied when
/// no direct conversion is available.
/// Source is a base unit. Dest is any unit with the
/// same dimensions.
#define BOOST_UNITS_DEFAULT_CONVERSION(Source, Dest) \
namespace boost { \
namespace units { \
template<> \
struct unscaled_get_default_conversion::type> \
{ \
BOOST_STATIC_CONSTEXPR bool is_defined = true; \
typedef Dest::unit_type type; \
}; \
} \
} \
void boost_units_require_semicolon()
/// Specifies the default conversion to be applied when
/// no direct conversion is available.
/// Params is a PP Sequence of template arguments.
/// Source is a base unit. Dest is any unit with the
/// same dimensions. The source must not be a scaled
/// base unit.
#define BOOST_UNITS_DEFAULT_CONVERSION_TEMPLATE(Params, Source, Dest) \
namespace boost { \
namespace units { \
template \
struct unscaled_get_default_conversion \
{ \
BOOST_STATIC_CONSTEXPR bool is_defined = true; \
typedef typename Dest::unit_type type; \
}; \
} \
} \
void boost_units_require_semicolon()
/// INTERNAL ONLY
/// Users should not create their units in namespace boost::units.
/// If we want to make this public it needs to allow better control over
/// the namespaces. --SJW.
/// template that defines a base_unit and conversion to another dimensionally-consistent unit
#define BOOST_UNITS_DEFINE_BASE_UNIT_WITH_CONVERSIONS(namespace_, name_, name_string_, symbol_string_, factor, unit, id)\
namespace boost { \
namespace units { \
namespace namespace_ { \
struct name_ ## _base_unit \
: base_unit { \
static BOOST_CONSTEXPR const char* name() { return(name_string_); } \
static BOOST_CONSTEXPR const char* symbol() { return(symbol_string_); } \
}; \
} \
} \
} \
BOOST_UNITS_DEFINE_CONVERSION_FACTOR(namespace_::name_ ## _base_unit, unit, double, factor); \
BOOST_UNITS_DEFAULT_CONVERSION(namespace_::name_ ## _base_unit, unit)
/// Find the conversion factor between two units.
template
inline
BOOST_CONSTEXPR
typename one_to_double_type<
typename detail::conversion_factor_helper::type
>::type
conversion_factor(const FromUnit&,const ToUnit&)
{
return(one_to_double(detail::conversion_factor_helper::value()));
}
} // namespace units
} // namespace boost
#endif // BOOST_UNITS_CONVERSION_HPP