UBU_bang_.html -- ACL2 Version 6.3

## UBU!

undo commands, without a query or an error

    Major Section:  HISTORY

    Example:
    :ubu! :x-4

The keyword command `:ubu!` is the same as `:``ubu`, but with related queries suppressed appropriately, and with a guarantee that it is ``error-free.'' More precisely, the error triple (see error-triples) returned by `:ubu!` will always be of the form `(mv nil val state)`. `:``Oops` will undo the last `:ubu!`. Also see ubu, see ubt, and see u.