Re: [boost] Progress of Boost.SVG_Plot

From: Cédric Venet (cedric.venet_at_[hidden])
Date: 2007-06-15 17:20:30

> // in user_header.hpp
> enum svg_user_customization { my_initial_style, ... };
> 
> svg_plot& operator<<(svg_plot& p, svg_user_customization val)
> {
>     switch(val)
>     {
>     case my_initial_style:
> 
[...]
        }
  }
> 
> // in user_program.cpp
> int main()
> {
>     svg_plot my_plot;
>     my_plot << my_initial_style;
> 
>     // work
> }
> 
> // end program
> 

Is there a raison to use an enumeration instead of a 'tag' type for
selecting the implementation? (if I am not clear, an example follow) using a
type would need to use () but can probably be more powerful. An example:

Class MyStyle {
Public:
        Explicit MyStyle(float BgClr):m_bg_clr(BgClr) {}

        Float get BgClr() {...}
Protected:
        float m_bg_clr;
};
Class AnotherStyle {};

svg_plot& operator<<(svg_plot& p, MyStyle val) {
        p << axis_on << color(val.getBgClr()) << ...
}

svg_plot& operator<<(svg_plot& p, AnotherStyle) {
        p << axis_off
}

Int main() {
        P << MyStyle(0.7) << plot();
        P << AnotherStyle() << truc;
        MyStyle s1(0.2);
        P << s1 << somethings;
}

> 2  Can it not be done other ways?
> p.line(t1,t2).line(t2,t3).line(t3,t1)?
> 
> 

We want the primitive (Triangle here) to be user defined, isn't it?

We could have
p.add<Triangle>(t1,t2,t3);
or
p.add(Triangle(t1,t2,t3));
or
p.add<Triangle>(t1)(t2)(t3);

but I don't really see the advantage over stream based interface.

> 
> 3  Are the set and stream methods mutually exclusive?
> programming practice (to maintain the header, you'd have to make the
> same
> changes to the interface to both the set_ and << functions)

One can call the other but the argument type would need to be duplicated

> 
> 4  Could this be used even if the set method was used for other
> parameters?
> 
> 
> Yes. However, combining my answers for #1 and #3, I think it would be
> best
> to keep them all in the stream interface.
> 

Personally, I found the streaming interface for adding object pretty good.
But I like the setter interface better for customizing the svg_plot. But it
isn't a very important choice in my eyes.

-- 
Cédric Venet