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

primrec
^^^^^^^^^

Basis Function Combinator


From the "Overview of the language JOY":

> The primrec combinator expects two quoted programs in addition to a
data parameter. For an integer data parameter it works like this: If
the data parameter is zero, then the first quotation has to produce
the value to be returned. If the data parameter is positive then the
second has to combine the data parameter with the result of applying
the function to its predecessor.::

    5  [1]  [*]  primrec

> Then primrec tests whether the top element on the stack (initially
the 5) is equal to zero. If it is, it pops it off and executes one of
the quotations, the [1] which leaves 1 on the stack as the result.
Otherwise it pushes a decremented copy of the top element and
recurses. On the way back from the recursion it uses the other
quotation, [*], to multiply what is now a factorial on top of the
stack by the second element on the stack.::

    n [Base] [Recur] primrec

       0 [Base] [Recur] primrec
    ------------------------------
          Base

         n [Base] [Recur] primrec
    ------------------------------------------ n > 0
       n (n-1) [Base] [Recur] primrec Recur



Gentzen diagram.


Definition
~~~~~~~~~~

if not basis.


Derivation
~~~~~~~~~~

if not basis.


Source
~~~~~~~~~~

if basis


Discussion
~~~~~~~~~~

Lorem ipsum.


Crosslinks
~~~~~~~~~~

Lorem ipsum.


