PLOGHELP LEASH                               Simon Nichols, October 1990

    ?- leash.
    ?- leash(Port).

Evaluable predicate which enables user interaction at spy-ports.

Whenever the control flow of a procedure with a spy-point set reaches a
"leashed" spy-port, a debugging message is printed and you will be
prompted for some response (see PLOGHELP * SPY for the available
options). At an "unleashed" port, the debugging message is still
printed, but execution then continues immediately without prompting.

The evaluable predicate leash/0 leashes all spy-ports which are
currently unleashed.

The evaluable predicate leash/1 leashes the port or ports identified by
its argument: this should be one of the four spy-port names 'call',
'exit', 'redo' or 'fail' or a list of the same.

The predicates leash/0 and leash/1 are implemented in terms of the more
general spy_action/2, specifying the "stop" action.


-- Related documentation ----------------------------------------------

PLOGHELP * SPY
 How to set spy-points on predicates in order to debug them

PLOGHELP * SPY_ACTION
 Predicate which changes the action of the debugger at spy-ports

PLOGHELP * UNLEASH
 Predicate which disables user interaction at spy-points


--- C.all/plog/help/leash
--- Copyright University of Sussex 1992. All rights reserved. ----------