fail). The atom
allrefers to all ports. If the port is preceded by a
sign the trace-point is cleared for the port. If it is preceded by a
the trace-point is set.
The predicate trace/2 activates debug mode (see debug/0). Each time a port (of the 4-port model) is passed that has a trace-point set the goal is printed as with trace/0. Unlike trace/0 however, the execution is continued without asking for further information. Examples:
|Trace all ports of hello with any arity in any module.|
|Trace failures of foo/2 in any module.|
|Stop tracing bar/1.|
The predicate debugging/0 shows all currently defined trace-points.
debug. See also debug/0.
unify. The special shorthand
allrefers to all ports,
fullrefers to all ports except for the unify port (default).
halfrefers to the
unknown. Values are
fail. If the
unknownflag is set to
warning, unknown/2 reports the value as
Currently available options are:
|on||read_clause/1 (used by consult/1) warns on variables only appearing once in a term (clause) which have a name not starting with an underscore.|
|on||read/1 and derivatives will produce an error message on quoted atoms or strings longer than 5 lines.|
|off||Accept dollar as a lower case character, thus avoiding the need for quoting atoms with dollar signs. System maintenance use only.|
|on||Warn if the clauses for a predicate are not together in the same source file.|
compatibility. See the prolog-flag