lambda with templates
template <class in, class out, class T>
out stransform(in b, in e, out d, T p(const T&)) {
    while (b != e)
        *d++ = p(*b++);
    return d;
}

stransform(begin(vec1), end(vec1), back_inserter(vec2), predi<double>);

stransform(begin(vec1), end(vec1), back_inserter(vec2), [] (double x) ->double {return x * 10;} );

template <class in, class out, class UnaryPredicate>
out stransform(in b, in e, out d, UnaryPredicate p);

stransform (
    begin (vec1),
    end (vec1),
    back_inserter (vec2),
    [] (const double & x) -> double {
        return x * 10;
    });

template<class InputIterator, class OutputIterator, class Functor>
OutputIterator
transform(InputIterator begin, InputIterator end, OutputIterator out, Functor f);

// function declaration
int increment(int);

int array[] = { 0, 1, 2, 3, 4 };
transform(std::begin(array), std::end(array), std::begin(array), increment);

template<typename InputIterator, typename OutputIterator, typename Functor>
OutputIterator
transform(InputIterator begin, InputIterator end, OutputIterator out, Functor f);