Logtalk

<h2 id="features">Features</h2>
<p>Logtalk aims to bring together the advantages of object-oriented programming and logic programming.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> Object-orientation emphasizes developing discrete, reusable units of software, while logic programming emphasizes representing the knowledge of each object in a declarative way.
</p><p>As an object-oriented programming language, Logtalk's major features include support for both <a href="/facts/Class_(computer_science)/zvzkSAtE">classes</a> (with optional <a href="/facts/Metaclass/qIUSeeLa">metaclasses</a>) and <a href="/facts/Prototype-based_programming/x9oNIYPG">prototypes</a>, parametric objects,<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> <a href="/facts/Protocol_(object-oriented_programming)/jDMpXoLN">protocols</a> (<a href="/facts/Interface_(object-oriented_programming)/jDMpXoLN">interfaces</a>), categories (components, <a href="/facts/Aspect-oriented_programming/HK7CFwan">aspects</a>, <a href="/facts/Software_hot_patch/sIHVBPls">hot patching</a>), <a href="/facts/Multiple_inheritance/kFvNb9rY">multiple inheritance</a>, public/protected/private inheritance, <a href="/facts/Event-driven_programming/QlGL2Fu6">event-driven programming</a>, high-level multi-threading programming,<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> <a href="/facts/Reflection_(computer_science)/Nj8stFfp">reflection</a>, and automatic generation of documentation.
</p><p>For Prolog programmers, Logtalk provides wide portability, featuring predicate <a href="/facts/Namespace/9efXwMtV">namespaces</a> (supporting both static and dynamic objects), public/protected/private object predicates, <a href="/facts/Coinduction/chs1pWP7">coinductive predicates</a>, separation between interface and implementation, simple and intuitive meta-predicate semantics, <a href="/facts/Lambda_calculus/DaD3RuQ4">lambda expressions</a>, <a href="/facts/Definite_clause_grammar/8KKqd15p">definite clause grammars</a>, term-expansion mechanism, and conditional compilation. It also provides a module system based on de facto standard core module functionality (internally, modules are compiled as prototypes).
</p>
<h2 id="examples">Examples</h2>
<p>Logtalk's syntax is based on Prolog:
</p>
?- write('Hello world'), nl.
Hello world
true.

<p>Defining an object:
</p>
:- object(my_first_object).

:- initialization((write('Hello world'), nl)).

:- public(p1/0).
    p1 :- write('This is a public predicate'), nl.

:- private(p2/0).
    p2 :- write('This is a private predicate'), nl.

:- end_object.

<p>Using the object, assuming is saved in a my_first_object.lgt file:
</p>
?- logtalk_load(my_first_object).
Hello world
true.

?- my_first_object::p1.
This is a public predicate
true.

<p>Trying to access the private predicate gives an error:
</p>
?- my_first_object::p2.
ERROR: error(permission_error(access, private_predicate, p2), my_first_object::p2, user)

<h3>Anonymous functions</h3>
<p class="note">This section is an excerpt from <a href="/facts/Examples_of_anonymous_functions/JmeU3owQ">Examples of anonymous functions § Logtalk</a>.[<a href="https://en.wikipedia.org/w/index.php?title=Examples_of_anonymous_functions&action=edit#Logtalk">edit</a>]</p>
<p>Logtalk uses the following syntax for anonymous predicates (lambda expressions):
</p>
{FreeVar1, FreeVar2, ...}/[LambdaParameter1, LambdaParameter2, ...]>>Goal

<p>A simple example with no free variables and using a list mapping predicate is:
</p>
| ?- meta::map([X,Y]>>(Y is 2*X), [1,2,3], Ys).
Ys = [2,4,6]
yes

<p>Currying is also supported. The above example can be written as:
</p>
| ?- meta::map([X]>>([Y]>>(Y is 2*X)), [1,2,3], Ys).
Ys = [2,4,6]
yes

<h2 id="prolog-back-end-compatibility">Prolog back-end compatibility</h2>
<p>Supported back-end Prolog compilers include <a href="/facts/BProlog/YNdk95TL">B-Prolog</a>, <a href="/facts/Ciao_(programming_language)/cqdD9zuc">Ciao Prolog</a>, CxProlog, <a href="/facts/ECLiPSe/Nbt3Lpjj">ECLiPSe</a>, <a href="/facts/GNU_Prolog/6a0LeK7Y">GNU Prolog</a>, JIProlog, <a href="/facts/Quintus_Prolog/jvAyP6Gg">Quintus Prolog</a>, Scryer Prolog, <a href="/facts/SICStus_Prolog/r5h66Qh1">SICStus Prolog</a>, <a href="/facts/SWI-Prolog/4krpcVnm">SWI-Prolog</a>, Tau Prolog, Trealla Prolog, <a href="/facts/XSB/5KT45Htw">XSB</a>, and <a href="/facts/YAP_(Prolog)/0Wk4fnRB">YAP</a>.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> Logtalk allows use of back-end Prolog compiler libraries from within object and categories.
</p>
<h2 id="developer-tools">Developer tools</h2>
<p>Logtalk features on-line help, a documenting tool (that can generate PDF and HTML files), an entity diagram generator tool, a built-in debugger (based on an extended version of the traditional Procedure Box model found on most Prolog compilers), a unit test framework with code coverage analysis, and is also compatible with selected back-end Prolog profilers and graphical tracers.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a>
</p>
<h2 id="applications">Applications</h2>
<p>Logtalk has been used to process <a href="/facts/ISO_10303-21/WlGoNt7m">STEP</a> data models used to exchange <a href="/facts/Product_manufacturing_information/lgbyw1To">product manufacturing information</a>.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a>  It has also been used to implement a reasoning system that allows preference reasoning and <a href="/facts/Constraint_solving/oKCeIV2L">constraint solving</a>.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a>
</p>
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Mercury_(programming_language)/4UDPmoxe">Mercury (programming language)</a></li>
<li><a href="/facts/Oz_(programming_language)/Fsb7wHsv">Oz (programming language)</a></li>
<li><a href="/facts/Prolog%252B%252B/2qxLmJA2">Prolog++</a></li>
<li><a href="/facts/Visual_Prolog/03tnjaK8">Visual Prolog</a></li>
<li><a href="/facts/Comparison_of_Prolog_implementations/eQHFInTs">Comparison of Prolog implementations</a></li>
<li><a href="/facts/Prolog_syntax_and_semantics/umbG3kbq">Prolog syntax and semantics</a></li></ul>

<h2 id="external-links">External links</h2>
<ul><li><a href="https://logtalk.org">Official website</a></li>
<li><a href="https://logtalk.org/blog.html">Logtalking blog</a></li>
<li>From Plain Prolog to Logtalk Objects: Effective Code Encapsulation and Reuse (Invited Talk). Paulo Moura. Proceedings of the 25th International Conference on Logic Programming (ICLP), July 2009. LNCS 5649. Springer-Verlag Berlin Heidelberg". (<a href="https://logtalk.org/papers/iclp2009/logtalk_iclp2009.pdf">Slides</a>)</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Paulo Moura (2003). Logtalk: Design of an Object-Oriented Logic Programming Language. PhD thesis. Universidade da Beira Interior <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>Paulo Moura (2003). Logtalk: Design of an Object-Oriented Logic Programming Language. PhD thesis. Universidade da Beira Interior <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Paulo Moura (2003). Logtalk: Design of an Object-Oriented Logic Programming Language. PhD thesis. Universidade da Beira Interior <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>Paulo Moura (2003). Logtalk: Design of an Object-Oriented Logic Programming Language. PhD thesis. Universidade da Beira Interior <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>Moura, Paulo (2011). Programming Patterns for Logtalk Parametric Objects. Applications of Declarative Programming and Knowledge Management. Lecture Notes in Computer Science. Vol. 6547. doi:10.1007/978-3-642-20589-7_4. ISBN 978-3-642-20588-0. <a href="978-3-642-20588-0" target="_blank">978-3-642-20588-0</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
<li id="fn:6"><p>Practical Aspects of Declarative Languages. Lecture Notes in Computer Science. Vol. 4902. 2008. doi:10.1007/978-3-540-77442-6. ISBN 978-3-540-77441-9. <a href="978-3-540-77441-9" target="_blank">978-3-540-77441-9</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li>
<li id="fn:7"><p>"Logtalk compatibility". Logtalk.org. 2016-10-10. Retrieved 2021-07-06. <a href="https://logtalk.org/compatibility.html" target="_blank">https://logtalk.org/compatibility.html</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li>
<li id="fn:8"><p>"Developer Tools – LogtalkDotOrg/logtalk3 Wiki – GitHub". Github.com. 2013-02-12. Retrieved 2013-08-19. <a href="https://github.com/LogtalkDotOrg/logtalk3/wiki/Developer-Tools" target="_blank">https://github.com/LogtalkDotOrg/logtalk3/wiki/Developer-Tools</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li>
<li id="fn:9"><p>Logic Programming. Lecture Notes in Computer Science. Vol. 4079. 2006. doi:10.1007/11799573. ISBN 978-3-540-36635-5. <a href="978-3-540-36635-5" target="_blank">978-3-540-36635-5</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li>
<li id="fn:10"><p>Victor Noël; Antonis Kakas (2009). Gorgias-C: Extending Argumentation with Constraint Solving (PDF). Logic Programming and Nonmonotonic Reasoning. Lecture Notes in Computer Science. Vol. 5753. pp. 535–541. <a href="ftp://ftp.irit.fr/IRIT/SMAC/DOCUMENTS/PUBLIS/lpnmr-09_noel-kakas.pdf" target="_blank">ftp://ftp.irit.fr/IRIT/SMAC/DOCUMENTS/PUBLIS/lpnmr-09_noel-kakas.pdf</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li>
</ol>

Logtalk open-in-new

Logtalk