REVAPPEND.html -- ACL2 Version 6.3

### REVAPPEND

concatentate the reverse of one list to another

    Major Section:  ACL2-BUILT-INS

`(Revappend x y)` concatenates the reverse of the list `x` to `y`, which is also typically a list.

The following theorem characterizes this English description.

    (equal (revappend x y)
           (append (reverse x) y))

Hint: This lemma follows immediately from the definition of `reverse` and the following lemma.

    (defthm revappend-append
      (equal (append (revappend x y) z)
             (revappend x (append y z))))

The guard for `(revappend x y)` requires that `x` is a true list.

`Revappend` is defined in Common Lisp. See any Common Lisp documentation for more information.

To see the ACL2 definition of this function, see pf.