Lisp2k

Lisp2k is an participation in the essies2004 competition / event. It tries to combine all the power of Lisp with a modern, 21st century environment, while remaining true to its real goals (this is supposed to be esoteric programming). In particular, it features:

• programs that can (and must) inspect themselves at runtime;
• a handy symbol value type;
• a mutable symbol table for globals, enabling you to build a reflective programming enrironment;
• excellent support for dynamic scoping;
• I/O facilities comparable to those of Common Lisp;
• relatively good macro support, no added hygiene;
• low on syntax, letting you define all those wonderful weird characters to do your own favourite stuff ™!
• modern pseudo-markup for program structure, especially indentation sensitivity ^_^
• dynamic typing
• and last, but not least, a good portion of those famous quote unquote services.

On the other hand, Lisp2k is:

based on a Forth-like evaluator

functions, not their callers, decide how much parameters they get. Notation is Lispishly prefix, though. Lisp2k does not re-evaluate expressions after evaluation, you have to request that yourself. This sometimes makes composing functions tricky.

intended to be a minimal system

the primitive operations of Lisp2k are few, even more so than for ordinary Lisps. For example, there is no (car). (Lisp2k tries to gain new ground in the Turing Tarpit art, extending the functional world away for idemponent environments like the lambda calculus.)

properly tail recursive

Lisp2k does not have primitives for looping, so this is a must.

not natively equipped with a REP loop

you could write one, though. A reader and printer are already available. Lisp2k lacks all other kinds of runtime services, too. Implementing a proper support library might be a future project.

intended to be hard to use, yet provide powerful abstractions

in the field of esoteric programming languages, most really-hard-to-use ones have been imperative, and promising rivals on the functional side have had automatic code generators available. Lisp2k is meant to be sufficiently far from well-known research areas so as to prevent trivial mappings from a well-known formalism to Lisp2k.

natively pattern-matching

Pattern matching helps to reduce the number of primitives in the language. Besides, it's a Good Thing™.

I hope you're enthusiastic to get your hands dirty with Lisp2k. More detailed information is available in Lisp2k language reference.