Revisiting_the_Admission_of_App.html -- ACL2 Version 6.3

## Revisiting the Admission of App

Here is the definition of `app` again with certain parts highlighted. If you are taking the Walking Tour, please read the text carefully and click on each of the links below, except those marked . Then come back here.

    ACL2 !>(defun app (x y)
      (cond ((endp x) y)
            (t (cons (car x)
                     (app (cdr x) y)))))

    The admission of APP is trivial, using the
    relation O<  (which is known to be well-founded on
    the domain recognized by O-P ) and the measure
    (ACL2-COUNT  X).  We observe that the
    type of APP is described by the theorem (OR
    (CONSP (APP X Y)) (EQUAL (APP X Y) Y)).  We used primitive type
    reasoning.

    Summary
    Form:  ( DEFUN APP ...)
    Rules: ((:FAKE-RUNE-FOR-TYPE-SET NIL))
    Warnings:  None
    Time:  0.03 seconds (prove: 0.00, print: 0.00, other: 0.03)
     APP