-----Original Message----- On Behalf Of Brian Braatz a(nonintegral) sequence?
"Brian Braatz" <brianb@rmtg.com> writes:
I am looking for a way to basically do this:
typedef vector<int,float,float,char,int,int,int,double> types; typedef vector<int,float,char, double> expected; typedef unique_all< types, is_same<_1,_2> >::type result;
BOOST_MPL_ASSERT(( equal< result,expected > ));
(note the examples I am using use integral types, in my situation
I am
not using integral types)
[David Abrahams Writes:]
If you don't need to preserve order, just stick them in an mpl::set<>. In fact, you might be able to use a set<> to begin with and just skip the vector<>.
Otherwise, I would write a little algorithm based on the implementation of remove_if (which you can find nicely described in the online reference manual). Instead of passing along a predicate at each stage of the fold<>, pass along a set<> that accumulates the elements you've already seen. When the next element is already in
GOT IT! see below: the
set<>, skip it.
Try working that out for yourself; it'll be good for you ;-)
[Brian Braatz Writes:] OK I finally figured this out, thanks in BIG PART to David sending me down the right path of thinking. I am also going to save this mail, and double back around at some point and write this by hand. (I still a little shaky with the full bore compile time recursion code- and (as David suggests) this would be an excellent way to get better) I have written a small sample and am including it in this mail. I am doing this for the benefit of someone in the future searching the list archives looking for a solution. here is the working solution: this sample takes a list of types in a sequence and removes the duplicate types struct A {}; struct B {}; struct C {}; struct D {}; void RemoveDupsFromSequence() { // 10 elements in dups, but only 4 unique types typedef vector<B,D,A,B,C,B,D,B,C,C>::type dups; // copy it into a set<>, // the insert<> applied to set<> will // ensure the same type cannot be added twice typedef copy< dups , inserter< set< >, insert<_1,_2 > > >::type result; // Prints 10 cout << "dups size " << mpl::size<dups>::value << endl; // Prints 4 - result is now something like set<A,B,C,D> // Note: actual order is unknown\indeterminate for result cout << "result size " << mpl::size<result>::value << endl; } BIG THANKS to David Abrahams :) Brian