Re: [Swig-user] C++ functions with all arguments optional = bug? (Python)

On 23/02/11 11:30, Jacob F. wrote:
> Hi,
>
> I'm getting somewhat odd behavior when wrapping C++ functions that have
> all arguments optional.
>
> C++ header definition for the function talked about below:
> struct display {
> ...
> void draw(float = 0, float = 0, float = 1, float = NULL, float = NULL,
> float = 0, float = NULL);
> ...
> }
>
> A normal class::function looks like this in the outputted module .py file:
> def draw(self, *args) -> "void" : return _scge.display_draw(self, *args)
>
> But when all arguments are optional it looks like this...
> def draw(self, arg0 : 'float' = 0, arg1 : 'float' = 0, arg2 : 'float' = 1,
> arg3 : 'float' = None, arg4 : 'float' = None,
> arg5 : 'float' = 0, arg6 : 'float' = None) -> "void" : return
> _scge.display_draw(self, arg0, arg1, arg2, arg3, arg4, arg5, arg6)
>
> Now if I call display.draw() or with any arguments it gives an error:
>    File "/media/Field/lb/pybin/scge.py", line 285, in draw
>      arg5 : 'float' = 0, arg6 : 'float' = None) -> "void" : return
> _scge.display_draw(self, arg0, arg1, arg2, arg3, arg4, arg5, arg6)
> NotImplementedError: Wrong number of arguments for overloaded function
> 'display_draw'.
>    Possible C/C++ prototypes are:
>      draw(display *,float,float,float,float,float,float,float)
>      draw(display *,float,float,float,float,float,float)
>      draw(display *,float,float,float,float,float)
>      draw(display *,float,float,float,float)
>      draw(display *,float,float,float)
>      draw(display *,float,float)
>      draw(display *,float)
>      draw(display *)
>
>
> If I change that line in the outputted module .py file to read:
> def draw(self, *args) -> "void" : return _scge.display_draw(self, *args)
>
> ...then I can call display.draw() fine.
>
> Is this a bug?  Or something I'm doing wrong? That could be the case as
> I've only just started using SWIG 2 days ago, loving it too btw.
>
This is a bug. Please put it in the SourceForge bug tracker. Strange one 
as well, it has something to do with the default value, as this fails:

struct display {
void draw(float = NULL) {}
};

and this works as expected:

struct display {
void draw(float = 0) {}
};

If you can't modify the headers you are wrapping, please workaround it 
using:
%feature("compactdefaultargs") display::draw;

William