SWI-Prolog
A comprehensive Prolog environment, probably the gold standard of such.
SWI-Prolog offers a comprehensive free Prolog environment.
Since its start in 1987, SWI-Prolog development has been
driven by the needs of real world applications.
SWI-Prolog is widely used in research and education
as well as commercial applications."Its main author is Jan Wielemaker.
The name SWI is derived from Sociaal-Wetenschappelijke Informatica
("Social Science Informatics"), the former name of the group at
the University of Amsterdam, where Wielemaker is employed.
{% aTargetBlank "https://www.swi-prolog.org", "SWI-Prolog" %}
is implemented in C (48%) and Prolog (39%).
To install the terminal command swipl in macOS,
enter brew install swi-prolog
To start a SWI-Prolog top level from a terminal, enter swipl.
To specify configuration for all top level sessions,
create the file $HOME/.config/swi-prolog/init.pl.
For example, this file might set prolog flags.
SWI-Prolog Execution
To enter and run Prolog code in a web browser using SWI-Prolog,
browse SWISH.
Enter facts and rules in the left pane.
Enter a query in the lower-right pane.
Press the "Run!" button or ctrl-return to execute the query.
SWI-Prolog Conformance
SWI-Prolog adds features beyond the ISO standard,
some of which contradict the standard, making it non-conforming.
One example is the addition of a string type.
Many dedicated predicates are needed to operate on these strings
rather than using list predicates.
Another example is the addition of a custom dict type.
It is very easy to write code that runs in SWI-Prolog,
but does not run in other Prolog implementations.
In addition, some code that is valid according to the ISO standard
does not run in SWI-Prolog.
For a detailed take on this issue, see {% aTargetBlank
"https://www.youtube.com/watch?v=kGQNeeRp4sM", "Preparing Prolog" %}.
Also see {% aTargetBlank
"https://www.complang.tuwien.ac.at/ulrich/iso-prolog/SWI7_and_ISO",
"SWI7 and ISO Prolog" %}.
SWI-Prolog Packs
Packs are add-on libraries.
To see a list of known packages, browse {% aTargetBlank
"https://www.swi-prolog.org/pack/list",
"Packs (add-ons) for SWI-Prolog" %}.
Alternatively, enter pack_list(substring) where
substring is part of one or more pack names.
To install a pack, enter pack_install(name).
This will download the code and install it.
The "reif" pack (reified if) implements the if_ predicate
which is similar to the -> operator, but has some advantages.
See the section "Higher-order Predicates" for examples.
The {% aTargetBlank "https://www.swi-prolog.org/pack/list?p=gvterm",
"gvterm" %} pack generates a graphviz file from a Prolog term.
This is useful for visualizing the tree structure of a term.
SWI-Prolog Debugging
For information on using the debugger in SWI-Prolog, see {% aTargetBlank
"https://www.swi-prolog.org/pldoc/man?section=debugoverview",
"Overview of the Debugger" %}.
The trace predicate enables tracing of the search to find a query solution.
The following code defines fact about my family and a rule about grandfathers.
female(amanda).
female(judi).
female(tami).
male(jeremy).
male(mark).
male(richard).
father(richard, mark).
father(mark, amanda).
father(mark, jeremy).
mother(judi, mark).
mother(tami, amanda).
mother(tami, jeremy).
grandfather_of(X, Y) :-
father(X, P),
(father(P, Y); mother(P, Y)).
To trace the execution of the query grandfather_of(richard, X).,
enter trace. and then the query.
The screenshot below shows the output.
After each line in the trace, press the spacebar
to advance to the next term to be evaluated.
After a solution is found, press the semicolon key or the spacebar
to begin searching for the next solution.
The trace predicate enables both the trace and debug modes.
To disable these, enter notrace. and nodebug.
SWI-Prolog Executables
To compile a Prolog source file to an executable,
enter swipl -o {exe-name} -c {source-name}.pl.
For example, swipl -o sukuko -c suduko.pl.
Running this executable with ./suduko starts a top level session
and loads the compiled facts and rules.
Other SWI-Prolog-related
"Creating Web Applications in SWI-Prolog"
"yet another web applications tutorial" | "Writing a blog using SWI Prolog" storing to Postgresql as the storage.
"How to create a web service easily?"
Tags: language logic prolog
Last modified 16 December 2024