[ePiX-devel] Re: Stable release (Version 1.2.0)

[Maik Beckmann]

Am Mittwoch, 26. September 2007 16:55:38 schrieb Andrew D. Hwang:
> As I understand it, the new syntax accepts the same arguments as the old
> (so is not more restrictive to the user), and is slightly more efficient: 
> Both implementations copy u, but the second carries the small overhead of
> passing a const reference for the first argument. 

passing something as const reference is faster than non-const reference. The 
performance cost comes from the added temporary P tmp(u).  But this minimal 
runtime overhead (a triple is a very small object) isn't an issue for epix 
IMHO.

> Please let me know if 
> this is incorrect, particularly, if there are argument types that work as
> expected with the old syntax but not with the new.

I'm afraid it isn't valid, consider:

void foo(P const& p1, P const& p2)
{
   P mid = 0.5*(p1 + p2);
  // where + has the signature
  // P operator+(P lhs, P const& rhs);
}

This dosn't work, since p1 is const and you can't pass a const object as 
no-const (the opposite: passing a non-const as const works).

Btw. at some places you wrote things like
  double  foo(const double arg);
which is very uncommon.  This signature
  double  foo(double arg);
which is used is some place like:
    bar()
    {
        double feed= ...;
        double feed_copy = feed;
        double myfoo = foo(feed);
        feed == feed_copy // is allway true!!
    }
keeps feed allways untouched, since its passed by value.


Regards, Maik


PS: Can you add a hatching example? It doesn't work for me so far.