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|prolog_trace.pl -- Print access to predicates|
This library prints accesses to specified predicates by wrapping the predicate.
Module:Name/Arity(or `//Arity for non-terminals), both the module and arity may be omitted in which case Pred refers to all matching predicates. PortSpec is either a single port (
redo), preceded with
-or a list of these. The predicate modifies the current trace specification and then installs a suitable wrapper for the predicate using wrap_predicate/4. For example:
?- trace(append). % lists:append/2: [all] % lists:append/3: [all] % append/1: [all] true. ?- append([a,b], [c], L). T  Call: lists:append([a, b], [c], _18032) T  Call: lists:append([b], [c], _19410) T  Call: lists:append(, [c], _20400) T [28 +0.1ms] Exit: lists:append(, [c], [c]) T [19 +0.2ms] Exit: lists:append([b], [c], [b, c]) T [10 +0.5ms] Exit: lists:append([a, b], [c], [a, b, c]) L = [a, b, c]. ?- trace(append, -all). % lists:append/2: Not tracing % lists:append/3: Not tracing % append/1: Not tracing
The text between  indicates the call depth (first number) and for
all ports except the
call port the wall time since the start
(call port) in milliseconds. Note that the instrumentation and print
time is included in the time. In the example above the actual time
is about 0.00001ms on todays hardware.
The following predicates are exported, but not or incorrectly documented.