Logtalk 2.37.1

Logtalk is a mature Open Source object-oriented logic programming language that can use most Prolog implementations as a back-end compiler.

Main features:
- Predicate directives (declarations) may be contained inside protocols (interfaces), which may be implemented by any object.
- Object names can be compound terms containing free variables that can be used to parametrize object predicates. This allows us to treat any predicate as an instantiation of a parametric object. I.e. through parametric object we can associate any number of methods with a compound term.
- You may have, in the same application, class-based hierarchies (with instantiation and specialization relations) and prototype-based hierarchies (with extension relations). Moreover, fundamental language features such as protocols (interfaces) and categories (components) can be used simultaneously by classes, instances, and prototypes.
- No need to be constrained to a single, lengthy hierarchy rooted in some generic object.
- Logtalk supports private, protected, and public inheritance in a way similar to C . Moreover, any entity relation can be qualified using a scope keyword. E.g. an object can privately implement a protocol, thus making all protocol declared predicates private.
- Set the scope of your object predicates to match your protocol design and let the runtime system enforce your choices.
- Objects can be either static or dynamic. Static objects are defined in source files which are compiled and loaded in the same way as Prolog files. Dynamic object can be either defined in source files or created at runtime.
- Any static object may contain both static and dynamic predicates.
- Logtalk uses standard Prolog syntax with the addition of a few operators and directives for a smooth learning curve. Prolog code can be easily encapsulated inside objects with little or no changes. Moreover, Logtalk can transparently interpret most Prolog modules as Logtalk objects for easy reusing of existing code (e.g. libraries).
- Predicates can be implicitly called when a spied event occurs, allowing programming solutions which minimize object coupling. In addition, events provide support for behavioral reflection.
- Predicates can be encapsulated inside categories, which can be virtually imported by any object, without any code duplication and irrespective of object hierarchies. Thus, objects may be defined through composition of categories, which act as fine-grained units of code reuse.
- High level multi-threading programming is available when running Logtalk with selected back-end Prolog compilers, allowing objects to support both synchronous and asynchronous messages. Easily take advantage of modern multi-processor and multi-core computers without bothering with the details of creating and destroying threads, implement thread communication, or synchronizing threads.
- Logtalk supports multi-inheritance of both protocol and implementation. An object may implement several protocols and extend, specialize, or instantiate several objects. Multi-inheritance conflicts are solved implicitly by the Logtalk lookup algorithms or explicitly by using predicate directives.
- Logtalk code is compiled using the same technics that you use to write efficient Prolog code. In addition, Logtalk supports both static binding and dynamic binding (with method lookup caching), greatly improving performance. Benchmark results for some Prolog compilers are available here.
- Logtalk is designed for smooth integration with any Prolog compiler that conforms or closely follows the ISO Prolog Standard.
- Logtalk interfaces with a specific back-end Prolog compiler via a minimal configuration file making it compatible with almost any modern compiler.
- Logtalk automatically generates a documentation file in XML format for every compiled object, protocol, or category. The system includes all the necessary XSL(T) files and scripts to convert documenting files to (X)HTML and PDF.

System requirements:
- Prolog

Enhancements
- Added support for declaring and defining object and category multifile predicates. This new feature is primarily intended to facilitate migration of Prolog code to Logtalk and should be used with caution as multifile support is spotty among back-end Prolog compilers (easily leading to portability problems). Multifile predicates can be both static or dynamic.
- Added support for compiling clauses for module multifile predicates within objects and categories in order to provide better integration with CLP(FD) and similar constraint packages.
- Added support for parsing module/2 directives whose export list contains operator declarations.
- Improved Logtalk compiler error-checking of file-level op/3 directives.
- Updated the Logtalk compiler to try to detect calls to proprietary built-in meta-predicates not declared in the config files. Detection may fail due to the lack of standardization of meta-predicate specifications.
- Updated the Logtalk compiler to avoid unexpected compilation errors when querying predicate properties due to the lack of standardization of the Prolog predicate_property/2 built-in predicate.
- Improved runtime error-checking for meta-calls whose closure argument is either Object:Closure or Module:Closure.
- Corrected a Logtalk compiler bug where a redefinition of a proprietary built-in meta-predicate (declared in the config files) would be ignored.
- Corrected a bug in the implementation of the Logtalk