Re: Optimzed vs. readable code

[Pierre THIERRY <nowhere dot man at levallois dot eu dot org>]

Scribit caj@cs.york.ac.uk dies 30/11/2005 hora 16:53:
> > The thing is, in CS courses on compilation, one can learn that it is
> > nowadays a so classic optimization that one can safely expect it
> > from any decent compiler.
> Really? It is trivial in the case of a pointer, or say a
> vector::iterator, which is just a thin wrapper over a pointer. I
> expect it gets much harder for types with more complex iterators.

I don't see the point. I repeat: i would not have even proposed the
modification if I wasn't expecting any decent compiler to do the
following optimization:

	void foo(Iterator first, Iterator last)
	{
		Iterator current = first;
		for ( ; current != last; ++current)
			do_something(current);
		}
	}

becomes:

	void foo(Iterator first, Iterator last)
	{
		for ( ; first != last; ++first)
			do_something(first);
		}
	}

So there won't be any one side-effect more than with the current
implementation. FWIW, in the STL I can see (shipped with GCC 4.0.3), the
iterators are already passed by value, so if copying them will trigger
side-effects, it already does...

I don't use them often (never used them, indeed...), but I suspect a
reference could used also:

	Iterator & current = first;

Carefully,
Nowhere man
-- 
nowhere.man@levallois.eu.org
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