Re: [boost] Re: rationals initialization bug

From: Lutz Kettner (kettner_at_[hidden])
Date: 2000-11-28 22:24:59

Hi Paul,

> I agree up to a point. But I take a slightly more extreme view, that there
> should be no construction from double at all. This is based on my not seeing
> any use for it, admittedly. Your example seems to indicate that there is a
> (rare) use for an exact conversion, but in general I feel that it would be
> surprising more often than useful.

Yes, there is a good use in geometry, the data comes often in doubles
(after reading it from a file or so). For example 3d meshes in graphics.
So I would like to see the (exact) constructor from double, but I can
also perfectly understand if it will be a cast-like function call.

With CGAL we like to use LEDA (the library at 
http://www.mpi-sb.mpg.de/LEDA/leda.html, not the language) that has 
good number types. They convert doubles to leda_real and also 
to leda_rational with constructors. I don't know internals though.

Best regards,

Lutz