Lusynth is a structural editor and inline evaluator for a purely functional dialect of Lisp.
The code being edited is represented as an AST and modified based on keystrokes, always preserving a syntactically valid structure. As the code changes, it is re-evaluated and each reduction step is shown or summarized.
All keyboard input is appended to a file and can be replayed to restore the current or any previous application state.
After the basic implementation is complete, future work will focus on better editing controls and reduction summaries.