function D = addClosuresToDiffOp(D, closures)
    for i = 1:size(closures,1)
        for j = 1:size(closures,2)
            closure = closures{i,j};
            if ~isa(closure, 'function_handle')
                closure = @(v) closure*v;
            end
            D = @(v) D(v) + closure(v);
        end
    end
end