Re: [Lib2geom-devel] Templates

[Nathan H. <nj...@nj...>]

On Mon, Jun 16, 2014 at 01:57:26AM +0200, Krzysztof Kosi??ski wrote:
> 2014-06-16 0:01 GMT+02:00 Johan Engelen <jbc...@sw...>:
> > Hi all,
> >    I am reading Modern C++ Design by Andrei Alexandrescu and already
> > after the first few pages, I want to start work on 2geom that I've been
> > thinking about for a while. Would like to hear your thoughts,
> > encouragement or otherwise :-)

...
> Furthermore, this would require changing many functions that take
> Point to template functions taking Point<Coord>. We would effectively
> need to lift most of 2Geom code into headers.

Yes, I thought about this when we started, and mental and I discussed
this at length.  Here are the reasons against:

* as Krzysztof says, templates mean everything must be on the compile
  path for everything.
* More complex methods for everything
* Ugly error messages
* Minor performance cost
* Slower compiles (a big issue for me - the slower the compile the
  slower the development)

I couldn't think of any other compelling reasons for (especially when you
consider that D2<T> does what you want).

> > Point<double> is just the start. My endgoal is to be able to choose
> > Path<CubicBezier>: a path for which all functions know that it is just a
> > vector with CubicBeziers, allowing SIMD optimization of many operations
> > on it. Instead of the Path<Curve> that we have now, that does not allow
> > for any of that.
> 
> This would be interesting. Path could also have a second parameter
> specifying the underlying structure: vector, list or an
> order-statistic tree.

I suspect it would be hard to get useful optimisations this way.

> Another interesting area of improvement would be to put the node-based
> path representation from the node editor in 2Geom, though this would
> need extra effort to decouple it from the display and event handling
> code.

Jaberto is thinking about this a little bit.  Perhaps he could say
something to this.

njh