[C++-sig] Re: Making copy of function derived from C++ pure virtual function

[David Abrahams]

Paul F. Kunz wrote:
>   I replaced the file
> 
> ftp://ftp.slac.stanford.edu/users/pfkeb/abrahams/HippoDraw-1.12.7.tar.gz
> 
> With one that illustrates the clone() problem.   One file, one script,
> no threads.   

Paul, I've take a look, but you really could make my life easier.  I
don't need makefiles or (worse) autoconf ".in" files.  I don't need
subdirectories.  I just want a .cpp (not .cxx, if we're going to pick
nits) and a .py file.  You could strip out all the extraneous macros too.

Traceback (most recent call last):
  File "c:\boost\libs\python\user\hippo/fitting.py", line 32, in ?
    f.test()
TypeError: __init__() takes exactly 1 argument (2 given)
[5611 refs]

So your problem is really simple.  In cloning the Linear object you've
created, its __init__ method is getting called with *another* Linear
object that should be the source of the clone operation.  But your
Linear's __init__ function only takes one argument, as the error message
says.

If you want to pass through both default construction and copy
construction, you have to write something like:

    def __init__ ( self, other = None ):
        if other:
            FunctionBase.__init__(self, other)
        else:
            FunctionBase.__init__(self)

But then, this is boring; why don't you leave off the __init__ function
altogether?  Then the one(s) supplied by FunctionBase will get called.

-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com