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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]
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