Re: [eigen] Namespaces

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Benoît Jacob wrote:
On Thursday 11 October 2007 11:46:54 Andre Krause wrote:
Cyrille Berger wrote:
On Wednesday 10 October 2007, Benoît Jacob wrote:
we initially used namespaces, but switched to prefixing recently. The
reason is that namespace offer little protection as most users will want
to be "using namespace". For instance look at the EiObject class.
Without prefix, it'd be Object. A much too common name. If we
encapsulate it in a namespace, it becomes Eigen::Object, which is safe,
but... most users would like to "using namespace Eigen" and if some
class is called "Object" then "using namespace" is not an option,
because "Object" is a too polluting name.
In that case the compiler would return an error, it's hardly a problem.

Look at what Qt does. Qt classes are not encapsulated in any namespace,
instead they have the Q prefix, like "QObject".
Qt was first release at a time when namespaces were not well (if at all)
supported by most C++ compiler.
why not make the eigen namespace name shorter?

instead of Eigen::Vector<float,4>, just

ei::Vector<float,4> ...

it just looks better / more modern than EiVector...
and if it is that short, one is less tempted to use "using namespace".

and finally, it is no problem to use some typedefs.

so i personally would rather like to see the prefix "Ei" removed.. but
well, i could also easily life with the prefix. its just a bit uglier.

It's really a matter of taste. Some people will prefer EiVector because it's shorted. Some other people will prefer Ei::Vector because the :: is more evocative. In any case, the namespacing is just a special kind of prefixing. So here we're only discussing prefix aesthetics -- we could go on forever.

And I'm not sure with what you mean with "it is no problem to use some typedefs", but did you know, C++ doesn't allow cross-namespace typedefs. So

namespace A { class B; }
typedef A::B C;

shouldn't compile.

oh - wasnt aware of this.

but after reading your other posts, i think you are right: it seems to be
just a matter of taste and makes absolutely no difference, if using namespaces
or prefixes.

keep on your great work!

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