Features

CLAIRE provides automatic memory allocation/de-allocation, which would have prevented an easy implementation as a C++ library. Also, set-oriented programming is much easier with a set-oriented language like CLAIRE than with libraries. CLAIRE is about ten years old and the current version reaches a new level of maturity.

CLAIRE is a high-level language that can be used as a complete development language, since it is a general purpose language, but also as a pre-processor to C++ or Java, since a CLAIRE program can be naturally translated into a C++ program (We continue to use C++ as our target language of choice, but the reader may now substitute Java to C++ in the rest of this document). CLAIRE is a set-oriented language in the sense that sets are first-class objects, typing is based on sets and control structures for manipulating sets are parts of the language kernel. Similarly, CLAIRE makes manipulating lists easy since lists are also first-class objects. Sets and lists may be typed to provide a more robust and expressive framework. CLAIRE can also be seen as a functional programming language, with full support for lambda abstraction, where functions can be passed as parameters and returned as values, and with powerful parametric polymorphism.

CLAIRE is an object-oriented language with single inheritance. As in SMALLTALK, everything that exists in CLAIRE is an object. Each object belongs to a unique class and has a unique identity. Classes are the corner stones of the language, from which methods (procedures), slots and tables (relations) are defined. Classes belong themselves to a single inheritance hierarchy. However, classes may be grouped using set union operators, and these unions may be used in most places where a class would be used, which offers an alternative to multiple inheritance. In a way similar to Modula-3, CLAIRE is a modular language that provides recursively embedded modules with associated namespaces. Module decomposition can either be parallel to the class organization (mimicking C++ encapsulation) or orthogonal (e.g., encapsulating one service among multiple classes).

CLAIRE is a typed language, with full inclusion polymorphism. This implies that one can use CLAIRE with a variety of type disciplines ranging from weak typing in a manner that is close to SMALLTALK up to a more rigid manner close to C++. This flexibility is useful to capture programming styles ranging from prototyping to production code development. The more typing information available, the more CLAIRE's compiler will behave like a statically typed language compiler. This is achieved with a rich type system, based on sets, that goes beyond types in C++. This type system provides functional types (second-order types) similar to ML, parametric types associated to parametric classes and many useful type constructors such as unions or intervals. Therefore, the same type system supports the naive user who simply wishes to use classes as types and the utility library developer who needs a powerful interface description language.

[XL] Starting with XL CLAIRE, CLAIRE is intended to cover various aspects of web oriented application (running in a CGI like environment), that is to serve dynamic content over the web. The Wcl syntax is introduced as new method of printing, in a similar way to printf but closer to the HTML syntax. The development of a web oriented agent would however require the module Wcl, not included in the standard XL CLAIRE distribution.