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/usr/lib/swipl/library/prolog_trace.pl
All Application Manual Name SummaryHelp

  • swipl
    • library
      • error.pl
      • debug.pl -- Print debug messages and test assertions
      • apply.pl -- Apply predicates on a list
      • lists.pl -- List Manipulation
      • broadcast.pl -- Event service
      • predicate_options.pl -- Access and analyse predicate options
      • shlib.pl -- Utility library for loading foreign objects (DLLs, shared objects)
      • option.pl
      • thread_pool.pl
      • gensym.pl
      • settings.pl
      • arithmetic.pl
      • main.pl -- Provide entry point for scripts
      • readutil.pl -- Read utilities
      • operators.pl -- Manage operators
      • pairs.pl -- Operations on key-value lists
      • prolog_source.pl -- Examine Prolog source-files
      • quasi_quotations.pl -- Define Quasi Quotation syntax
      • url.pl -- Analysing and constructing URL
      • www_browser.pl -- Open a URL in the users browser
      • prolog_colour.pl
      • record.pl -- Access compound arguments by name
      • prolog_xref.pl -- Prolog cross-referencer data collection
      • occurs.pl -- Finding and counting sub-terms
      • ordsets.pl -- Ordered set manipulation
      • assoc.pl -- Binary associations
      • ugraphs.pl -- Graph manipulation library
      • iostream.pl -- Utilities to deal with streams
      • atom.pl -- Operations on atoms
      • prolog_pack.pl -- A package manager for Prolog
      • solution_sequences.pl -- Modify solution sequences
      • git.pl -- Run GIT commands
      • ctypes.pl -- Character code classification
      • utf8.pl -- UTF-8 encoding/decoding on lists of character codes.
      • base64.pl -- Base64 encoding and decoding
      • persistency.pl -- Provide persistent dynamic predicates
      • pure_input.pl -- Pure Input from files and streams
      • nb_set.pl -- Non-backtrackable sets
      • aggregate.pl -- Aggregation operators on backtrackable predicates
      • csv.pl -- Process CSV (Comma-Separated Values) data
      • dialect.pl -- Support multiple Prolog dialects
      • apply_macros.pl -- Goal expansion rules to avoid meta-calling
      • yall.pl -- Lambda expressions
      • prolog_code.pl -- Utilities for reasoning about code
      • dif.pl -- The dif/2 constraint
      • thread.pl -- High level thread primitives
      • rbtrees.pl -- Red black trees
      • nb_rbtrees.pl -- Non-backtrackable operations on red black trees
      • random.pl -- Random numbers
      • sandbox.pl -- Sandboxed Prolog code
      • prolog_format.pl -- Analyse format specifications
      • pprint.pl -- Pretty Print Prolog terms
      • modules.pl -- Module utility predicates
      • lazy_lists.pl -- Lazy list handling
      • edinburgh.pl -- Some traditional Edinburgh predicates
      • prolog_clause.pl -- Get detailed source-information about a clause
      • prolog_breakpoints.pl -- Manage Prolog break-points
      • dicts.pl -- Dict utilities
      • check.pl -- Consistency checking
      • ansi_term.pl -- Print decorated text to ANSI consoles
      • backcomp.pl -- Backward compatibility
      • writef.pl -- Old-style formatted write
      • charsio.pl -- I/O on Lists of Character Codes
      • sort.pl
      • base32.pl -- Base32 encoding and decoding
      • tables.pl -- XSB interface to tables
      • statistics.pl -- Get information about resource usage
      • varnumbers.pl -- Utilities for numbered terms
      • prolog_jiti.pl -- Just In Time Indexing (JITI) utilities
      • intercept.pl -- Intercept and signal interface
      • terms.pl -- Term manipulation
      • quintus.pl -- Quintus compatibility
      • codesio.pl -- I/O on Lists of Character Codes
      • prolog_debug.pl -- User level debugging tools
      • listing.pl -- List programs and pretty print clauses
      • make.pl -- Reload modified source files
      • increval.pl -- Incremental dynamic predicate modification
      • strings.pl -- String utilities
      • date.pl -- Process dates and times
      • help.pl -- Text based manual
      • prolog_wrap.pl -- Wrapping predicates
      • rwlocks.pl -- Read/write locks
      • shell.pl -- Elementary shell commands
      • explain.pl -- Describe Prolog Terms
      • threadutil.pl -- Interactive thread utilities
      • prolog_versions.pl -- Demand specific (Prolog) versions
      • wfs.pl -- Well Founded Semantics interface
      • optparse.pl -- command line parsing
      • prolog_profile.pl -- Execution profiler
      • qsave.pl -- Save current program as a state or executable
      • zip.pl -- Access resource ZIP archives
      • heaps.pl -- heaps/priority queues
      • prolog_history.pl -- Per-directory persistent commandline history
      • when.pl -- Conditional coroutining
      • prolog_trace.pl -- Print access to predicates
        • trace/1
        • trace/2
        • tracing/2
        • list_tracing/0
        • notraceall/0
      • edit.pl -- Editor interface
      • prolog_stack.pl -- Examine the Prolog stack
      • prolog_codewalk.pl -- Prolog code walker
      • prolog_metainference.pl -- Infer meta-predicate properties
      • prolog_coverage.pl -- Coverage analysis tool
      • macros.pl -- Macro expansion
      • exceptions.pl -- Exception classification
      • oset.pl -- Ordered set manipulation
      • hashtable.pl -- Hash tables
      • coinduction.pl -- Co-Logic Programming
      • system.pl -- System utilities
      • prolog_autoload.pl -- Autoload all dependencies
      • prolog_config.pl -- Provide configuration information
      • portray_text.pl -- Portray text
      • win_menu.pl -- Console window menu
      • tty.pl -- Terminal operations
      • fastrw.pl -- Fast reading and writing of terms
      • files.pl
      • streams.pl -- Manage Prolog streams
 trace(:Pred) is det
 trace(:Pred, +PortSpec) is det
Print passes through ports of specified predicates. Pred is a, possible partial, specification of a predicate as it is also used be spy/1 and similar predicates. Where a full predicate specification is of the shape 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 (call, exit, fail or redo), preceded with + or - 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 [10] Call: lists:append([a, b], [c], _18032)
 T [19] Call: lists:append([b], [c], _19410)
 T [28] 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.

In addition, conditions may be specified. In this case the the specification takes the shape trace(:Head, Port(Condition)). For example:

?- trace(current_prolog_flag(Flag, Value), call(var(Flag))).
?- list_tracing.
% Trace points (see trace/1,2) on:
%     system:current_prolog_flag(A,_): [call(var(A))]

This specification will only print the goal if the registered condition succeeds. Note that we can use the condition for its side effect and then fail to avoid printing the event. Clearing the trace event on all relevant ports removes the condition. There is currently no way to modify the condition without clearing the trace point first.

ClioPatria (version V3.1.1-51-ga0b30a5)