- Reference manual
- The SWI-Prolog library
- library(aggregate): Aggregation operators on backtrackable predicates
- library(apply): Apply predicates on a list
- library(assoc): Association lists
- library(broadcast): Broadcast and receive event notifications
- library(charsio): I/O on Lists of Character Codes
- library(check): Consistency checking
- library(clpb): CLP(B): Constraint Logic Programming over Boolean Variables
- library(clpfd): CLP(FD): Constraint Logic Programming over Finite Domains
- library(clpqr): Constraint Logic Programming over Rationals and Reals
- library(csv): Process CSV (Comma-Separated Values) data
- library(debug): Print debug messages and test assertions
- library(error): Error generating support
- library(gensym): Generate unique identifiers
- library(iostream): Utilities to deal with streams
- library(lists): List Manipulation
- library(main): Provide entry point for scripts
- library(nb_set): Non-backtrackable set
- library(www_browser): Activating your Web-browser
- library(option): Option list processing
- library(optparse): command line parsing
- library(ordsets): Ordered set manipulation
- library(pairs): Operations on key-value lists
- library(persistency): Provide persistent dynamic predicates
- library(pio): Pure I/O
- library(predicate_options): Declare option-processing of predicates
- library(prolog_pack): A package manager for Prolog
- library(prolog_xref): Cross-reference data collection library
- library(quasi_quotations): Define Quasi Quotation syntax
- library(random): Random numbers
- library(readutil): Reading lines, streams and files
- library(record): Access named fields in a term
- library(registry): Manipulating the Windows registry
- library(simplex): Solve linear programming problems
- library(solution_sequences): Modify solution sequences
- library(tabling): Tabled execution (SLG)
- library(thread_pool): Resource bounded thread management
- library(ugraphs): Unweighted Graphs
- library(url): Analysing and constructing URL
- library(varnumbers): Utilities for numbered terms
- library(yall): Lambda expressions
- The SWI-Prolog library
- Reference manual
- Jan Wielemaker
This library is a replacement for format/3 for printing debug messages. Messages are assigned a topic. By dynamically enabling or disabling topics the user can select desired messages. Debug statements are removed when the code is compiled for optimization.
See manual for details. With XPCE, you can use the call below to start a graphical monitoring tool.
Using the predicate assertion/1 you can make assumptions about your program explicit, trapping the debugger if the condition does not hold.
- [nondet]debugging(?Topic, ?Bool)
- Examine debug topics. The form
debugging(+Topic)may be used to perform more complex debugging tasks. A typical usage skeleton is:
( debugging(mytopic) -> <perform debugging actions> ; true ), ...
The other two calls are intended to examine existing and enabled debugging tokens and are typically not used in user programs.
- Add/remove a topic from being printed.
nodebug(_)removes all topics. Gives a warning if the topic is not defined unless it is used from a directive. The latter allows placing debug topics at the start of a (load-)file without warnings.
For debug/1, Topic can be a term Topic > Out, where Out is either a stream or stream-alias or a filename (atom). This redirects debug information on this topic to the given output.
- List currently known debug topics and their setting.
- Specify additional context for debug messages. What is one of
+Context or -Context, and Context is one of
time(Format), where Format is a format specification for format_time/3 (default is
%T.%3f). Initially, debug/3 shows only thread information.
- [det]debug(+Topic, +Format, :Args)
- Format a message if debug topic is enabled. Similar to format/3
user_error, but only prints if Topic is activated through debug/1. Args is a meta-argument to deal with goal for the @-command. Output is first handed to the hook prolog:debug_print_hook/3. If this fails, Format+Args is translated to text using the message-translation (see print_message/2) for the term
debug(Format, Args)and then printed to every matching destination (controlled by debug/1) using print_message_lines/3.
The message is preceded by '% ' and terminated with a newline.
- See also
- [semidet,multifile]prolog:debug_print_hook(+Topic, +Format, +Args)
- Hook called by debug/3.
This hook is used by the graphical frontend that can be activated using prolog_ide/1:
- Acts similar to C
assert()macro. It has no effect if Goal succeeds. If Goal fails or throws an exception, the following steps are taken:
- [semidet,multifile]prolog:assertion_failed(+Reason, +Goal)
- This hook is called if the Goal of assertion/1
fails. Reason is unified with either
failif Goal simply failed or an exception call otherwise. If this hook fails, the default behaviour is activated. If the hooks throws an exception it will be propagated into the caller of assertion/1.