Experimental Physics and
Industrial Control System

Kay-Uwe Kasemir <[email protected]> · Mon, 26 Sep 2005 17:34:15 -0400

On Sep 26, 2005, at 14:12 , Jeff Hill wrote:

1) In your example you know at compile time that you want to

extract the

red, green, and blue properties out of some unknown PropertyCatalog.

Almost. I want the r, g, b under "color":
 catalog->color->red, ...
Who knows, the catalog might also contain
 catalog->preferred_display->foreground->color->red
 catalog->preferred_display->background->color->red
 catalog->beam->color->red
but I don't want any of those reds.

In your example, you expose a "red" property and
receive a "red" from the "incoming".
Which one would that be?

In this situation you have control over the content of MyColor and no

control over the content of catalogX. Since you have control over

MyColor

you can access it in any way MyColor sees fit - with blinding speed.
...
struct MyColor
{
public:
    void set ( const & PropertyCatalog );
private:
    int r, g, b;
    template < class VIEWER >
    static void traverse ( VIEWER & );
};

MyColor :: set ( const PropertyCatalog & incoming )
{
    ClassCatalog
        < MyColor, PropertyManipulator, traverse >
        manipulator ( *this );
    manipulator = incoming;
}

template < class VIEWER >
inline void MyColor :: traverse ( VIEWER & viewer )
{
    viewer.reveal ( colorRed, & MyColor::r );
    viewer.reveal ( colorGreen, & MyColor::g );
    viewer.reveal ( colorBlue, & MyColor::b );
}

...C++ templates are great for situations where the algorithm Is

the same, but the

data type varies. I can show you how to automate this if you are

interested

I'm purposedly avoiding the "locator" and templates at this stage
in order to see all that's happening.
When do you think the stringSegment will be usable?
It's the mayor thing missing to be able to play
with some more meaningful data.

Personally, the
getDouble()/getFloat/getInt/getUnsigned/getTime/getString/... type of
interface makes me nauseous.

Well, if we want to get down to what we're feeling,
I worry about the bend-over-and-expose-your-data approach.
That's almost a "paradigm".

-Kay

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System