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- [section boost/python/type_id.hpp]
- [section Introduction]
- <boost/python/type_id.hpp> provides types and functions for runtime type identification like those of of `<typeinfo>`. It exists mostly to work around certain compiler bugs and platform-dependent interactions with shared libraries.
- [endsect]
- [section Class template `type_info`]
- `type_info` instances identify a type. As `std::type_info` is specified to (but unlike its implementation in some compilers), `boost::python::type_info` never represents top-level references or cv-qualification (see section 5.2.8 in the C++ standard). Unlike `std::type_info`, `boost::python::type_info` instances are copyable, and comparisons always work reliably across shared library boundaries.
- ``
- namespace boost { namespace python
- {
- class type_info : totally_ordered<type_info>
- {
- public:
- // constructor
- type_info(std::type_info const& = typeid(void));
- // comparisons
- bool operator<(type_info const& rhs) const;
- bool operator==(type_info const& rhs) const;
- // observers
- char const* name() const;
- };
- }}
- ``
- [section Class template `type_info` constructor]
- ``type_info(std::type_info const& = typeid(void));``
- [variablelist
- [[Effects][constructs a `type_info` object which identifies the same type as its argument.]]
- [[Rationale][Since it is occasionally necessary to make an array of `type_info` objects a benign default argument is supplied. Note: this constructor does not correct for non-conformance of compiler `typeid()` implementations. See `type_id`, below.]]
- ]
- [endsect]
- [section Class template `type_info` comparison]
- ``bool operator<(type_info const &rhs) const;``
- [variablelist
- [[Effects][yields a total order over `type_info` objects.]]
- ]
- ``bool operator==(type_info const &rhs) const;``
- [variablelist
- [[Returns][`true` iff the two values describe the same type.]]
- [[Note][The use of `totally_ordered<type_info>` as a private base class supplies operators `<=`, `>=`, `>`, and `!=`]]
- ]
- [endsect]
- [section Class template `type_info` observers]
- ``
- char const* name() const;
- ``
- [variablelist
- [[Returns][The result of calling `name()` on the argument used to construct the object.]]
- ]
- [endsect]
- [endsect]
- [section Functions]
- ``
- std::ostream& operator<<(std::ostream&s, type_info const&x);
- ``
- [variablelist
- [[Effects][Writes a description of the type described by to `x` into s.]]
- [[Rationale][Not every C++ implementation provides a truly human-readable `type_info::name()` string, but for some we may be able to decode the string and produce a reasonable representation.]]
- [[Note][On some non-conforming C++ implementations, the code is not actually as simple as described above; the semantics are adjusted to work as-if the C++ implementation were conforming.]]
- ]
- ``
- template <class T> type_info type_id()
- ``
- [variablelist
- [[Returns][`type_info(typeid(T))`]]
- [[Note][On some non-conforming C++ implementations, the code is not actually as simple as described above; the semantics are adjusted to work as-if the C++ implementation were conforming.]]
- ]
- [endsect]
- [section Example]
- The following example, though silly, illustrates how the type_id facility might be used
- ``
- #include <boost/python/type_id.hpp>
- // Returns true iff the user passes an int argument
- template <class T>
- bool is_int(T x)
- {
- using boost::python::type_id;
- return type_id<T>() == type_id<int>();
- }
- ``
- [endsect]
- [endsect]
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