Reconciling positional and nominal binding

We define an extension of the simply-typed lambda-calculus where two different binding mechanisms, by position and by name, nicely coexist. In the former, as in standard lambda-calculus, the matching between parameter and argument is done on a positional basis, hence α-equivalence holds, whereas in the latter it is done on a nominal basis. The two mechanisms also respectively correspond to static binding, where the existence and type compatibility of the argument are checked at compile-time, and dynamic binding, where they are checked at run-time.