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Table of Contents
Models of the CallPolicies concept are used to specialize the behavior of Python callable objects generated by Boost.Python to wrapped C++ objects like function and member function pointers, providing three behaviors:
precall - Python argument
              tuple management before the wrapped object is invoked
            result_converter -
              C++ return value handling
            postcall - Python argument
              tuple and result management after the wrapped object is invoked
            extract_return_type
              - metafunction for extracting the return type from a given signature
              type sequence
            
          In order to allow the use of multiple models of CallPolicies in the same
          callable object, Boost.Python's CallPolicies class templates provide a
          chaining interface which allows them to be recursively composed. This interface
          takes the form of an optional template parameter, Base,
          which defaults to default_call_policies.
          By convention, the precall
          function of the Base is
          invoked after the precall
          function supplied by the outer
          template, and the postcall
          function of the Base is
          invoked before the postcall
          function of the outer template.
          If a result_converter is
          supplied by the outer template,
          it replaces any result_converter
          supplied by the Base. For
          an example, see return_internal_reference.
        
| Expression | Type | Result/Semantics | 
|---|---|---|
| 
                     | 
                    convertible to  | 
                    returns  | 
| 
                     | 
                    A model of  | An MPL unary Metafunction Class used produce the "preliminary" result object. | 
| 
                     | 
                    convertible to  | 
                     | 
| 
                     | A model of Metafunction. | 
                    An MPL unary Metafunction used extract the return type from a
                    given signature. By default it is derived from  |