The Pyka language is a Lisp language that uses first class environments to elegantly combined dynamic and lexical scoping. Common Lisp constructs like 'lambda' or 'defmacro' do not have a special status in this language but can be constructed from the Pyka language primitives. The function naming convention is based on the RSR7 (small) Scheme specification.
The idea behind the language is to expose the current environment of any expression being evaluated. Since we're implementing a Lisp language the environment can most easily be defined as a list of hash tables. Whenever a function is called a new hash table (holding the function arguments) is pushed onto the list, making the language inherently dynamically scoped. The current environment is always accessible through the special current-env callable, which returns the list of hash tables representing the environment. It turns out that such direct access to the environment, combined with the power of Fexpressions, and liberal use of the eval function allows us to implement lexical scoping!
This makes Pyka, as far as I know, the first language in which lexical scoping can be implemented as a library. Furthermore powerful programming constructs like macros can also be implemented directly without being part of the core language.
To run a REPL use:
pip3 install parsec
python3 ./src/bootstrap.py
This language is a work in progress so not currently very usable. I currently don't have much time to work on it actively. Please see /docs for programming constructs that will eventually be supported.