Advanced Control Options
These options are described in greater depth in dbg-bas-tra-ccf.
- retry --
This option restarts the current invocation. This may be useful when,
for example, you find yourself leaving with some incorrect result. When
a retry is performed, the invocation counter is reset so that counting
will continue from the current invocation number regardless of what
happened before the retry. This is in accord with the fact that
execution has returned to the state it was in at the time of the
original call. The message
% Retrying goal
is displayed to indicate where this occurred, in case you wish to follow
these numbers later.
- r i
- retry previous invocation --
If you supply an integer after the retry command, then this
is taken as specifying an invocation number and the system
tries to get you to the Call port, not of the current box,
but of the invocation box you have specified. This must be an ancestor
- fail --
This is similar to Retry except that it transfers control to the
Fail port of the current box. This places your execution in a
situation in which it is about to backtrack out of the current
invocation, having failed the goal.
- f i
- fail previous invocation --
This is similar to r i except that it transfers control to the
Fail port of the invocation specified (which must be an ancestor).