[C++-SIG] Re: blitz++ vs. NumPy?

[Paul F. Dubois]

-----Original Message-----
From: Phil Austin <phil at geog.ubc.ca>
Newsgroups: comp.lang.python

>
>2) Two things I wasn't able to figure out in 20 minutes are:
>
>  a) How to add my Blitz-based Py::Array constructor to Paul's code
>     using inheritence.  It looks like:
>
>    explicit Array (blitz::Array<int,1> dimens, PyArray_TYPES t =
PyArray_DOUBLE)
>        : Sequence(FromAPI(PyArray_FromDims(dimens.size(), dimens.data(),
t))) {
>        validate();
>    }
>
>  b) Is there a general way to convert between a Blitz TinyVector of
>     length N (where N isn't known at compile time)
>     and a blitz::Array<int,1>?  I'd like to avoid specifying the
>     dimensions to the Py::Array and the blitz::Array separately.
>
a. In C++ certain things are not inherited. These include the constructors
and copy constructors, and I think the assignment operator. In the CXX
documentation it gives you a list in the comments of the ones you have to
reimplement in a child. So the answer to your question is that you have to
copy my functions and change their names appropriately and put them in your
"child". You make a new child BlitzArray and give it appropriate
constructors, assignment, and destructors. You might want to just use Array
as a sample rather than a parent so that you can carefully manage the "tied"
memory without worrying about what I'm doing in Array. Note that since
~Object is virtual, the destructors are called up the inheritance line after
yours is executed. So you are ADDING actions rather than replacing them.

b. I don't know much about Blitz in detail and can't answer this question.
But you might be needing a member function template here to instantiate
something for each needed size. Unfortunately, that is the one area that has
the most portability problems at the moment.