mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2025-11-03 21:40:52 -05:00
329 lines
9.6 KiB
Plaintext
329 lines
9.6 KiB
Plaintext
[/
|
|
Copyright 2010 Neil Groves
|
|
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)
|
|
/]
|
|
[section:extending Extending the library]
|
|
|
|
[section:method_1 Method 1: provide member functions and nested types]
|
|
|
|
This procedure assumes that you have control over the types that should be made conformant to a Range concept. If not, see [link range.reference.extending.method_2 method 2].
|
|
|
|
The primary templates in this library are implemented such that standard containers will work automatically and so will __boost_array__. Below is given an overview of which member functions and member types a class must specify to be useable as a certain Range concept.
|
|
|
|
[table
|
|
[[Member function] [Related concept ]]
|
|
[[`begin()` ] [__single_pass_range__]]
|
|
[[`end()` ] [__single_pass_range__]]
|
|
]
|
|
|
|
Notice that `rbegin()` and `rend()` member functions are not needed even though the container can support bidirectional iteration.
|
|
|
|
The required member types are:
|
|
|
|
[table
|
|
[[Member type ] [Related concept ]]
|
|
[[`iterator` ] [__single_pass_range__]]
|
|
[[`const_iterator`] [__single_pass_range__]]
|
|
]
|
|
|
|
Again one should notice that member types `reverse_iterator` and `const_reverse_iterator` are not needed.
|
|
|
|
[endsect]
|
|
|
|
[section:method_2 Method 2: provide free-standing functions and specialize metafunctions]
|
|
|
|
This procedure assumes that you cannot (or do not wish to) change the types that should be made conformant to a Range concept. If this is not true, see [link range.reference.extending.method_1 method 1].
|
|
|
|
The primary templates in this library are implemented such that certain functions are found via argument-dependent-lookup (ADL). Below is given an overview of which free-standing functions a class must specify to be useable as a certain Range concept. Let `x` be a variable (`const` or `mutable`) of the class in question.
|
|
|
|
[table
|
|
[[Function ] [Related concept ]]
|
|
[[`range_begin(x)`] [__single_pass_range__]]
|
|
[[`range_end(x)` ] [__single_pass_range__]]
|
|
[[`range_calculate_size(x)`] [ Optional. This can be used to specify a mechanism for constant-time computation of the size of a range. The default behaviour is to return `boost::end(x) - boost::begin(x)` for random access ranges, and to return `x.size()` for ranges with lesser traversal capability. This behaviour can be changed by implementing `range_calculate_size` in a manner that will be found via ADL. The ability to calculate size in O(1) is often possible even with ranges with traversal categories less than random access.]]
|
|
]
|
|
|
|
`range_begin()` and `range_end()` must be overloaded for both `const` and `mutable` reference arguments.
|
|
|
|
You must also specialize two metafunctions for your type `X`:
|
|
|
|
[table
|
|
[[Metafunction ] [Related concept ]]
|
|
[[`boost::range_mutable_iterator`] [__single_pass_range__]]
|
|
[[`boost::range_const_iterator`] [__single_pass_range__]]
|
|
]
|
|
|
|
A complete example is given here:
|
|
|
|
``
|
|
#include <boost/range.hpp>
|
|
#include <iterator> // for std::iterator_traits, std::distance()
|
|
|
|
namespace Foo
|
|
{
|
|
//
|
|
// Our sample UDT. A 'Pair'
|
|
// will work as a range when the stored
|
|
// elements are iterators.
|
|
//
|
|
template< class T >
|
|
struct Pair
|
|
{
|
|
T first, last;
|
|
};
|
|
|
|
} // namespace 'Foo'
|
|
|
|
namespace boost
|
|
{
|
|
//
|
|
// Specialize metafunctions. We must include the range.hpp header.
|
|
// We must open the 'boost' namespace.
|
|
//
|
|
|
|
template< class T >
|
|
struct range_mutable_iterator< Foo::Pair<T> >
|
|
{
|
|
typedef T type;
|
|
};
|
|
|
|
template< class T >
|
|
struct range_const_iterator< Foo::Pair<T> >
|
|
{
|
|
//
|
|
// Remark: this is defined similar to 'range_iterator'
|
|
// because the 'Pair' type does not distinguish
|
|
// between an iterator and a const_iterator.
|
|
//
|
|
typedef T type;
|
|
};
|
|
|
|
} // namespace 'boost'
|
|
|
|
namespace Foo
|
|
{
|
|
//
|
|
// The required functions. These should be defined in
|
|
// the same namespace as 'Pair', in this case
|
|
// in namespace 'Foo'.
|
|
//
|
|
|
|
template< class T >
|
|
inline T range_begin( Pair<T>& x )
|
|
{
|
|
return x.first;
|
|
}
|
|
|
|
template< class T >
|
|
inline T range_begin( const Pair<T>& x )
|
|
{
|
|
return x.first;
|
|
}
|
|
|
|
template< class T >
|
|
inline T range_end( Pair<T>& x )
|
|
{
|
|
return x.last;
|
|
}
|
|
|
|
template< class T >
|
|
inline T range_end( const Pair<T>& x )
|
|
{
|
|
return x.last;
|
|
}
|
|
|
|
} // namespace 'Foo'
|
|
|
|
#include <vector>
|
|
|
|
int main(int argc, const char* argv[])
|
|
{
|
|
typedef std::vector<int>::iterator iter;
|
|
std::vector<int> vec;
|
|
Foo::Pair<iter> pair = { vec.begin(), vec.end() };
|
|
const Foo::Pair<iter>& cpair = pair;
|
|
//
|
|
// Notice that we call 'begin' etc with qualification.
|
|
//
|
|
iter i = boost::begin( pair );
|
|
iter e = boost::end( pair );
|
|
i = boost::begin( cpair );
|
|
e = boost::end( cpair );
|
|
boost::range_difference< Foo::Pair<iter> >::type s = boost::size( pair );
|
|
s = boost::size( cpair );
|
|
boost::range_reverse_iterator< const Foo::Pair<iter> >::type
|
|
ri = boost::rbegin( cpair ),
|
|
re = boost::rend( cpair );
|
|
|
|
return 0;
|
|
}
|
|
``
|
|
|
|
[endsect]
|
|
|
|
[section:method_3 Method 3: provide range adaptor implementations]
|
|
|
|
[section:method_3_1 Method 3.1: Implement a Range Adaptor without arguments]
|
|
|
|
To implement a Range Adaptor without arguments (e.g. reversed) you need to:
|
|
|
|
# Provide a range for your return type, for example:
|
|
``
|
|
#include <boost/range/iterator_range.hpp>
|
|
#include <boost/iterator/reverse_iterator.hpp>
|
|
|
|
template< typename R >
|
|
struct reverse_range :
|
|
boost::iterator_range<
|
|
boost::reverse_iterator<
|
|
typename boost::range_iterator<R>::type> >
|
|
{
|
|
private:
|
|
typedef boost::iterator_range<
|
|
boost::reverse_iterator<
|
|
typename boost::range_iterator<R>::type> > base;
|
|
|
|
public:
|
|
typedef boost::reverse_iterator<
|
|
typename boost::range_iterator<R>::type > iterator;
|
|
|
|
reverse_range(R& r)
|
|
: base(iterator(boost::end(r)), iterator(boost::begin(r)))
|
|
{ }
|
|
};
|
|
``
|
|
|
|
# Provide a tag to uniquely identify your adaptor in the `operator|` function overload set
|
|
``
|
|
namespace detail {
|
|
struct reverse_forwarder {};
|
|
}
|
|
``
|
|
|
|
# Implement `operator|`
|
|
``
|
|
template< class BidirectionalRng >
|
|
inline reverse_range<BidirectionalRng>
|
|
operator|( BidirectionalRng& r, detail::reverse_forwarder )
|
|
{
|
|
return reverse_range<BidirectionalRng>( r );
|
|
}
|
|
|
|
template< class BidirectionalRng >
|
|
inline reverse_range<const BidirectionalRng>
|
|
operator|( const BidirectionalRng& r, detail::reverse_forwarder )
|
|
{
|
|
return reverse_range<const BidirectionalRng>( r );
|
|
}
|
|
``
|
|
|
|
# Declare the adaptor itself (it is a variable of the tag type).
|
|
``
|
|
namespace
|
|
{
|
|
const detail::reverse_forwarder reversed = detail::reverse_forwarder();
|
|
}
|
|
``
|
|
|
|
[endsect]
|
|
|
|
[section:method_3_2 Method 3.2: Implement a Range Adaptor with arguments]
|
|
|
|
# Provide a range for your return type, for example:
|
|
``
|
|
#include <boost/range/adaptor/argument_fwd.hpp>
|
|
#include <boost/range/iterator_range.hpp>
|
|
#include <boost/iterator/transform_iterator.hpp>
|
|
|
|
template<typename Value>
|
|
class replace_value
|
|
{
|
|
public:
|
|
typedef const Value& result_type;
|
|
typedef const Value& argument_type;
|
|
|
|
replace_value(const Value& from, const Value& to)
|
|
: m_from(from), m_to(to)
|
|
{
|
|
}
|
|
|
|
const Value& operator()(const Value& x) const
|
|
{
|
|
return (x == m_from) ? m_to : x;
|
|
}
|
|
private:
|
|
Value m_from;
|
|
Value m_to;
|
|
};
|
|
|
|
template<typename Range>
|
|
class replace_range
|
|
: public boost::iterator_range<
|
|
boost::transform_iterator<
|
|
replace_value<typename boost::range_value<Range>::type>,
|
|
typename boost::range_iterator<Range>::type> >
|
|
{
|
|
private:
|
|
typedef typename boost::range_value<Range>::type value_type;
|
|
typedef typename boost::range_iterator<Range>::type iterator_base;
|
|
typedef replace_value<value_type> Fn;
|
|
typedef boost::transform_iterator<Fn, iterator_base> replaced_iterator;
|
|
typedef boost::iterator_range<replaced_iterator> base_t;
|
|
|
|
public:
|
|
replace_range(Range& rng, value_type from, value_type to)
|
|
: base_t(replaced_iterator(boost::begin(rng), Fn(from,to)),
|
|
replaced_iterator(boost::end(rng), Fn(from,to)))
|
|
{
|
|
}
|
|
};
|
|
``
|
|
|
|
# Implement a holder class to hold the arguments required to construct the RangeAdaptor.
|
|
The holder combines multiple parameters into one that can be passed as the right operand of `operator|()`.
|
|
``
|
|
template<typename T>
|
|
class replace_holder : public boost::range_detail::holder2<T>
|
|
{
|
|
public:
|
|
replace_holder(const T& from, const T& to)
|
|
: boost::range_detail::holder2<T>(from, to)
|
|
{ }
|
|
private:
|
|
void operator=(const replace_holder&);
|
|
};
|
|
``
|
|
|
|
# Define an instance of the holder with the name of the adaptor
|
|
``
|
|
static boost::range_detail::forwarder2<replace_holder>
|
|
replaced = boost::range_detail::forwarder2<replace_holder>();
|
|
``
|
|
|
|
# Define `operator|`
|
|
``
|
|
template<typename SinglePassRange>
|
|
inline replace_range<SinglePassRange>
|
|
operator|(SinglePassRange& rng,
|
|
const replace_holder<typename boost::range_value<SinglePassRange>::type>& f)
|
|
{
|
|
return replace_range<SinglePassRange>(rng, f.val1, f.val2);
|
|
}
|
|
|
|
template<typename SinglePassRange>
|
|
inline replace_range<const SinglePassRange>
|
|
operator|(const SinglePassRange& rng,
|
|
const replace_holder<typename boost::range_value<SinglePassRange>::type>& f)
|
|
{
|
|
return replace_range<const SinglePassRange>(rng, f.val1, f.val2);
|
|
}
|
|
``
|
|
|
|
[endsect]
|
|
|
|
[endsect]
|
|
|
|
[endsect]
|
|
|