The XL Programming Language

XL is a general purpose extensible programming language. The key word is extensible: XL can safely be extended through libraries and compiler plug-ins, in ways that are very difficult or limited with languages such as C++ or Java. This makes XL a good tool for concept programming.

XL borrowed ideas from quite a few languages: Ada, Basic, C, C++, C#, Eiffel, Erlang, Java, Intercal, Lisp, Pascal, Perl, Prolog, Python are some of the languages that were considered during its design. XL borrowed a lot from these respected ancestors, trying to at least incrementally improve over them. As a result, XL is believed to be, quite simply, the best programming language you can dream of today. If only the compiler was finished!

News: Now that the language became relatively stable and mature, I decided it was time to break everything, again. See the new development happening on the new XL web site for more info...

What does it look like?

A few examples of XL code, which should all compile with today's compiler, since they are part of the test suite:

• The infamous Hello World program. This program relies on a type-safe variable-arguments-list implementation of WriteLn (Pascal-style) in the library.
• A simple complex arithmetic module, with user-defined operators for common arithmetic operations on complex numbers. This module happens to generate very fast code on Itanium (70% faster than C++, with extra points for readability).
• The general Max and Min functions can take a variable number of arguments of any "ordered" type.
• The computation of a Julia set, with a fancy graphical display, seventies-style.

Secondary Objectives

The primary objective of XL is to be a good basis for concept programming. Additional objectives in designing the new language included:

• Making program maintenance easier, in particular by increasing readability.
• Enabling "programming in the large" for very large scale projects
• Supporting optimization on modern architectures, in particular where C and C++ semantics limit them. This is why, among others, pointers are nearly absent from the XL programming style.
• Creating a language which is both easy to implement and easy to learn.

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