ACL2-PC_colon__colon_UNDO.html -- ACL2 Version 6.3

### ACL2-PC::UNDO

(meta) `` undo some instructions

    Major Section:  PROOF-CHECKER-COMMANDS

    Examples:
    (undo 7)
    undo

    General Forms:

    (undo n) -- Undo the last n instructions.  The argument n should be
                a positive integer.

    undo     -- Same as (undo 1).

Remark: To remove the effect of an `undo` command, use `restore`. See the documentation for details.

Remark: If the argument `n` is greater than the total number of interactive instructions in the current session, then `(undo n)` will simply take you back to the start of the session.

The `undo` meta command always ``succeeds''; it returns `(mv nil t state)` unless its optional argument is supplied and of the wrong type (i.e. not a positive integer) or there are no instructions to undo.