2 question: Hi, i would like to know are there any easy way to do multi_array math operation on ones of same dimension and size.. #include <boost/multi_array.hpp> template <class T, int N> typename DimArray<T, N>::ndimarr array_minus(const typename DimArray<T, N>::ndimarr& A, const typename DimArray<T, N>::ndimarr& B) { typename DimArray<T, N>::ndimarr temp(A); typedef typename DimArray<T, N>::size TDS; const TDS outer_sz(A.size()); const TDS inner_sz(A[0].size()); for (TDS i = 0; i < outer_sz; ++i) { for (TDS j = 0; j < inner_sz; ++j) { temp[i][j] -= B[i][j]; } } return temp; } question 2: How do you find a index of an item where a specify condition is true. given this... template <class T> bool isSafe(const typename DimArray<T, 2>::ndimarr& MAX, const typename DimArray<T, 2>::ndimarr& Alloc, const typename DimArray<T, 2>::ndimarr& Need, const typename DimArray<T, 1>::ndimarr& Available) { typename DimArray<T, 1>::ndimarr Work(Available); typename DimArray<bool, 1>::ndimarr Finish(boost::extents[Need[0].size()]); typedef typename DimArray<T, 2>::size TDS; const TDS outer_sz(MAX.size()); const TDS inner_sz(MAX[0].size()); for(TDS i = 0; i < inner_sz; ++i) Finish[i] = false; } Is there a effective and safe way to find i such that Need[i] <= Work other than a loop. Thanks for the help.