--------------

app3
^^^^^^

Basis Function Combinator

Like app1 with three items.
    ::

             ... z y x [Q] . app3
        -----------------------------------
           ... [z ...] [Q] . infra first
               [y ...] [Q]   infra first
               [x ...] [Q]   infra first



Gentzen diagram.


Definition
~~~~~~~~~~

if not basis.


Derivation
~~~~~~~~~~

if not basis.


Source
~~~~~~~~~~

if basis


Discussion
~~~~~~~~~~

Lorem ipsum.


Crosslinks
~~~~~~~~~~

Lorem ipsum.


