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