[Pyrex] Too much overloading? And other stuff

[Edward C. Jones]

As you may have noticed by the questions I ask, I have had difficulties 
learning Pyrex. This is despite considerable programming experience in 
Python, C, and several other languages.

When I am a newbie, I get confused easily. One of the things in Pyrex 
that causes confusion for me is the four different meanings of "=". Here 
is a sample piece of code with the key C code output by "pyrexc".

def fun():
     cdef int i
     cdef int j
     i = 77     # __pyx_v_i = 77;
     j = i      # __pyx_v_j = __pyx_v_i;
     m = 88     # __pyx_1 = PyInt_FromLong(88); __pyx_v_m = __pyx_1;
     n = m      # __pyx_v_n = __pyx_v_m;
     i = m      # __pyx_2 = PyInt_AsLong(__pyx_v_m); __pyx_v_i = __pyx_2;
     n = j      #  __pyx_1 = PyInt_FromLong(__pyx_v_j); __pyx_v_n = __pyx_1;

There is a C assignment, a Python assignment and two conversions.

Also "." may be over overloaded. It has three meanings: C ".", C "->", 
and Python ".". Why were the C "*" (*p is the thing p is pointing at) 
and "->" operators eliminated?

My conclusion is that "things that are different should look different".

Today I Google searched for "programming language design philosophies". 
I found "Seven Deadly Sins if Introductory Programming Language Design" 
by Linda McIver and Damian Conway. The URL is 
"http://www.csse.monash.edu.au/~damian/papers/PDF/SevenDeadlySins.pdf". 
They call this problem "syntactic homonyms".

I suggest that Pyrex be strongly typed. In Python I never make mistakes 
because of the dynamic typing. But when C is around, it might be better 
to consistently use C's strong typing. Moreover, conversions should be
explicit. The result is

def fun():
     cdef int i
     cdef int j
     object m
     object n
     i = 77
     j = i
     m = 88
     n = m
     i = Cvar(m)
     n = object(j)

I also suggest Python/C++ style casting:

int i
float x
x = float(i)
i = int(x)

-------------------------------------------------------------------

I suggest a function type() or typeof() that works on both C and Python
variables.

-------------------------------------------------------------------

Here is a C macro that is difficult to wrap with Pyrex:

#define CV_IMAGE_ELEM( image, elemtype, row, col ) \
      (((elemtype*)((image)->imageData + (image)->widthStep*(row))[(col)]))

One of the macro variables is a type. It is feasible to eventually 
include some sort of C++ style templates in Pyrex? If necessary, Pyrex 
could generate C++ code.

-------------------------------------------------------------------

Buglet: Line 1980 of ExprNodes.py is

   error(self.pos, "Cannot take sizeof incomplete type '%s'" % arg_code)

The "arg_code" probably should be "arg_type".

Thanks,
Ed Jones