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[section boost/python/implicit.hpp]
[section Introduction]
`implicitly_convertible` allows Boost.Python to implicitly take advantage of a C++ implicit or explicit conversion when matching Python objects to C++ argument types.
[endsect]
[section Function template `implicit_convertible`]
``
template <class Source, class Target>
void implicitly_convertible();
``
[table
[[Parameter][Description]]
[[Source][The source type of the implicit conversion]]
[[Target][The target type of the implicit conversion]]
]
[variablelist
[[Requires][The declaration `Target t(s);`, where s is of type Source, is valid.]]
[[Effects][registers an rvalue `from_python` converter to Target which can succeed for any `PyObject* p` iff there exists any registered converter which can produce Source rvalues]]
[[Rationale][C++ users expect to be able to take advantage of the same sort of interoperability in Python as they do in C++.]]
]
[endsect]
[section Example]
In C++:
``
#include <boost/python/class.hpp>
#include <boost/python/implicit.hpp>
#include <boost/python/module.hpp>
using namespace boost::python;
struct X
{
X(int x) : v(x) {}
operator int() const { return v; }
int v;
};
int x_value(X const& x)
{
return x.v;
}
X make_x(int n) { return X(n); }
BOOST_PYTHON_MODULE(implicit_ext)
{
def("x_value", x_value);
def("make_x", make_x);
class_<X>("X",
init<int>())
;
implicitly_convertible<X,int>();
implicitly_convertible<int,X>();
}
``
In Python:
``
>>> from implicit_ext import *
>>> x_value(X(42))
42
>>> x_value(42)
42
>>> x = make_x(X(42))
>>> x_value(x)
42
``
[endsect]
[endsect]
|
