  Reductionism is a viable strategy for designing and implementing practical
programming languages, leading to solutions which are easier to extend,
experiment with and formally analyze. We formally specify and implement an
extensible programming language, based on a minimalistic first-order imperative
core language plus strong abstraction mechanisms, reflection and
self-modification features. The language can be extended to very high levels:
by using Lisp-style macros and code-to-code transforms which automatically
rewrite high-level expressions into core forms, we define closures and
first-class continuations on top of the core. Non-self-modifying programs can
be analyzed and formally reasoned upon, thanks to the language simple
semantics. We formally develop a static analysis and prove a soundness property
with respect to the dynamic semantics. We develop a parallel garbage collector
suitable to multi-core machines to permit efficient execution of parallel
programs.
