User-defined constraints including application of CHRs can be traced with the standard debugger. Debugging of the ECLiPSe code is done in the standard way. See the corresponding user manual for more information.
In order to use the debugging tool, the debug_compile flag
must have been on (default) during compilation (chr to
pl) and loading of the produced ECLiPSe code.
trace. activates the standard debugger
(tracing user-defined constraints like predicates).
chr_trace. activates the standard debugger
showing more information about the handling of constraints.
(application of CHRs).
chr_notrace. stops either debugger.
The debugger displays user-defined constraints and application of CHRs. User-defined constraints are treated as predicates and the information about application of CHRs is displayed without stopping. See the subsection on how CHRs work for an example trace. The additional ports are:
add: A new constraint is added to the constraint store.already_in: A constraint to be added was already present.
The ports related to application of rules are:
try_rule: A rule is tried.delay_rule: The last tried rule cannot fire because the guard did not succeed.fire_rule: The last tried rule fires.
The ports related to labeling are:
try_label: A label_with declaration is checked.delay_label: The last label_with declaration delays because the guard did not succeed.fire_label: The last tried label_with declaration succeeds,
so the clauses of the associated constraint will be used for built-in labeling.
When displayed, each constraint
is labelled with a unique integer identifier. Each rule is labelled
with its name as given in the chr source using the @
operator. If a rule does not have a name, it is displayed together
with a unique integer identifier.