Update documentation

doc/mp11/algorithm.qbk

@@ -244,4 +244,12 @@ for the elements of `L<U1...>` and `mp_false` for the elements of `L<U2...>`. Re
 `mp_any_of<L, P>` is `mp_true` when `P` holds for at least one element of `L`, `mp_false` otherwise. When `L` is empty, the result is `mp_false`.
 [endsect]
 
+[section `mp_for_each<L>(f)`]
+    template<class L, class F> constexpr F mp_for_each(F&& f);
+
+`mp_for_each<L>(f)` calls `f` with `mp_identity<T>()` for each element `T` of the list `L`, in order.
+
+Returns `std::forward<F>(f)`.
+[endsect]
+
 [endsect:algorithm]