On Friday 26 April 2002 13:37, Aleksey Gurtovoy wrote:
Toon Knapen wrote:
I have a list of heterogeneous objects, e.g. [snip sample code]
And now I want to have a function that can accumulate the value sof all the objects in the tuple, e.g. (pseudocode since my problem is exacly that I can't figure out how to code this)
template < typename TypleType > int accumulate_values(const TupleType& t) { int acc = 0; for(int i = 0 ; i < t.size() ; ++i ) acc += (get< i >( t )).value(); }
Can I do this using mpl (mpl looks great but I can't figure out how to do this).
It's not exactly a part of MPL (the library doesn't target "run-time" stuff to that extent yet; I hope it will some day), but "tuple extension" components I wrote some time ago (http://groups.yahoo.com/group/boost/files/tuple_ext/tuple_ext-08-nov-01.zi p ) allow one to do exactly these kinds of things: [snip aleksey's solution]
Thanks, I like tuple_ext a _lot_ ! It would be great to have complete STL-like functionality like this. I created an accumulate function (similar to the STL one) (see below) I also had to change your for_each. Actually, as in the STL, the unary-function does not necessarily need to be const so I removed the const. And finally, I also removed the friend declaration in the tuple_iterator since it complains about an implicit friend declaration to itself when using an iterator in a const-member function (gcc 2.95.3 and 3.x) Plans on adding this tuple_ext to the CVS ? toon [Non-text portions of this message have been removed]