Re: [Boost-users] [tr1] maximum number of allowed tuple elements?

From: Markus Werle (numerical.simulation_at_[hidden])
Date: 2008-08-25 08:12:04

John Maddock <john <at> johnmaddock.co.uk> writes:

> Markus Werle wrote:
> > Hi!
> >
> > Maybe I overlooked this portion of the docs, so could you please
> > give me a hint, whether and how one can set the maximum number of
> > tuple elements.
> 
> Ah... what the TR says is "The maximum number of elements in one tuple type 
> (clause 6.1) is implementation defined. This limit should be at least 10."

Then it would be very nice if the standard defined a MACRO allowing
me to determine the maximum number of tuple elements.
Otherwise this renders tr1::tuple completely useless for any template code.

> So you can't change it, or portably store more than 10 elements.  Of course 
> if you just happen to be using the Boost implementation then all the 
> Boost.Fusion macros and extensions kick in, but you can't guarentee that: to 
> take one example VC9+sp1 supplies it's own TR1 tuple so that's what 
> Boost.TR1 pulls in (out of necessity).

Yes. I was aiming at getting std::portable ...
These "implementation defined" clauses suck (not only IMHO).
It is like those "maximum nesting level of 18 in templates" that hinders 
portability for RealWorld apps.

Thinking about variadic template arguments while releasing a TR that
clings to fixed numbers seems odd to me ...

regards,

Markus