| Logtalk | |
| Paradigm: | Logic programming, object-oriented programming, prototype-based programming |
| Designer: | Paulo Moura |
| Latest Release Version: | 3.66.0 |
| Operating System: | Cross-platform |
| License: | Artistic License 2.0 (2.x) / Apache License 2.0 (3.01.x) |
| Influenced By: | Prolog, Smalltalk, Objective-C |
Logtalk is an object-oriented logic programming language that extends and leverages the Prolog language with a feature set suitable for programming in the large.[1] It provides support for encapsulation and data hiding, separation of concerns and enhanced code reuse. Logtalk uses standard Prolog syntax with the addition of a few operators and directives.
The Logtalk language implementation is distributed under an open source license and can run using a Prolog implementation (compliant with official and de facto standards) as the back-end compiler.
Logtalk aims to bring together the advantages of object-oriented programming and logic programming. Object-orientation emphasizes developing discrete, reusable units of software, while logic programming emphasizes representing the knowledge of each object in a declarative way.
As an object-oriented programming language, Logtalk's major features include support for both classes (with optional metaclasses) and prototypes, parametric objects,[2] protocols (interfaces), categories (components, aspects, hot patching), multiple inheritance, public/protected/private inheritance, event-driven programming, high-level multi-threading programming,[3] reflection, and automatic generation of documentation.
For Prolog programmers, Logtalk provides wide portability, featuring predicate namespaces (supporting both static and dynamic objects), public/protected/private object predicates, coinductive predicates, separation between interface and implementation, simple and intuitive meta-predicate semantics, lambda expressions, definite clause grammars, 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).
Logtalk's syntax is based on Prolog:
Defining an object:
- 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.
Using the object, assuming is saved in a my_first_object.lgt file:
?- my_first_object::p1.This is a public predicatetrue.
Trying to access the private predicate gives an error:
Supported back-end Prolog compilers include B-Prolog, Ciao Prolog, CxProlog, ECLiPSe, GNU Prolog, JIProlog, Quintus Prolog, Scryer Prolog, SICStus Prolog, SWI-Prolog, Tau Prolog, Trealla Prolog, XSB, and YAP.[4] Logtalk allows use of back-end Prolog compiler libraries from within object and categories.
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.[5]
Logtalk has been used to process STEP data models used to exchange product manufacturing information.[6] It has also been used to implement a reasoning system that allows preference reasoning and constraint solving.[7]