C ++ Boost valarray

Question

I am looking for a convenient and optimized way to compare 2 valarrays for equality. I've seen that Boost somewhat supports that:

In /boost/accumulators/numeric/functional/valarray.hpp --

// for "promoting" a std::valarray<bool> to a bool, useful for
// comparing 2 valarrays for equality:
//   if(numeric::promote<bool>(a == b))
template<typename From>
struct promote<bool, From, void, std_valarray_tag>
: std::unary_function<From, bool> {
    bool operator ()(From &arr) const {
        BOOST_MPL_ASSERT((is_same<bool, typename From::value_type>));
        for(std::size_t i = 0, size = arr.size(); i != size; ++i) {
            if(!arr[i]) {
                return false;
            }
        }
        return true;
    }
};

The following trivial code runs with std::valarray :

#include <valarray>
typedef std::valarray<int>    valarray_t;

int main(void) {
    int arr_length = 30; int num_of_idx = 5;
    // initialize arr
    int* arr = new int[arr_length];
    for (int i=0; i<arr_length; i++)
        arr[i] = i;
    // Create a valarray of ints.
    valarray_t vi(arr, arr_length);
    std::valarray<bool> aaa = ( vi == vi );
}

How can I check whether aaa is all true by using Boost?

Thanks!

Answer 1

The comment in your quoted code says exactly that:

bool allTrue = boost::numeric::promote<bool>(aaa);

Or just with C++11's standard library:

bool allTrue = std::all_of(begin(aaa), end(aaa), [](bool b){return b;});