[Pyrex] Re: C++, references, deref a pointer...

[Lenard Lindstrom]

On 8 Apr 2006 at 12:25, John Sutherland wrote:

> <Sorry for being non-threaded.. My procmail rules seem to have eaten  
> your response..>
> 
>  >> Approx line 1576 was:
>  >> if entry.is_variable or entry.is_cmethod:
>  >> to
>  >> if entry.is_variable or entry.is_cmethod or entry.is_cfunction:
>  >>
>  >I do not understand this change. An extension class attribute cannot
>  >be a C function. It can be a C function pointer, which is just a C
>  >attribute. See below.
> 
> I was actaully, trying to follow an older example you had done here:  
> http://lists.copyleft.no/pipermail/pyrex/2005-November/001518.html
> 
In the example:

   ctypedef struct myclass "MyClass":
        int dosomething(float arg)

should have been:

   ctypedef struct myclass "MyClass":
        int (* dosomething)(float arg)

I apologize for the typo and the confusion it has caused. My patches 
were never intended to add C++ features to the Pyrex language. 
Fortunately,  tricks such as declaring C++ methods as Cstructure 
field function pointers and using C name specifiers such as "new 
SomeClass" allow one to do method calls as well as deal with 
overloaded functions and operators. It is cheating a little, but it 
does avoid the necessity of writing C++ wrapper code when one does 
not have to handle C++ exceptions.

> In order for that to work, I had to add that small hack.. As I said,  
> it worked for me..
> 
Neat.

[snip] 
> 	void (*test1 "test") (int)
> 	void (*test2 "test") (float)
[snip]
> 
> cdef class Test	
> 	def __init__(self):
> 		self.thisptr = TestFactory()
> 	def test1(self,i):
> 		self.thisptr.test1(i)
> 	def test2(self,a,b):
> 		self.thisptr.test2(a,b)
> 
> I'm sure there's other ways, but this is how *i* solved it for now :)
> 
This is the only way I know to handle function/method overloading in 
Pyrex.

I guess I could have included a quick guide to using C++ within Pyrex 
with one of my patches. But then the first patch was simply to get 
some Pyrex module, any module, to compile as C++. The second patch 
was to get Pyrex to pass its test suite in C++. Between the two the 
idea never occurred to me. However, the cpptest.pyx example included 
with the first patch covers what I know.

Lenard Lindstrom
<len-l at telus.net>