[C++-SIG] (Still) confused about wrapping C++ types with CXX

[Barry Scott]

Steve,

	Maybe this is the time to try and put a FAQ together.

	Some of what you are asking seems to come down the following
	questions:

	Q1: How does Python get its first object from the C++ application?

	A1: Starting point objects will be returned from attributes of a
	module. The attributes can be variables or functions.

	Q2: Object X exposes a list/map of object Y

	A2A: Make a copy of the C++ list/map as a Python list/map. Each
	value in the list/map will be a wrapper around a C++ object Y.

	A2B: Add methods to the wrapping of object X that allow typical
	operations on the list/map.

	A2C: Add a wrapper object that forwards the Python list/map operations
	into the list/map exposed by object X.

	Which of A2A, A2B or A3C that applies depends on the nature of the
	list/map that is exposed.

	Q3: Can I have many wrappers around a single C++ object instance?

	A3a: No if you expect the Python code to be able to compare object
	identities. Arrange that the same wrapper is return for each unique
	C++ object whose identity is critical for the applications operation.

	A3b: Yes if object identity is not important.

	Q4: How should function sequence_XXX/map_XXX be implemented?

	A4: The implementation depends on the semantics of the C++ objects
	API that is being exposed as a sequence or map. There isn't a
	generic answer.

			BArry