I am also writting my own toy lisp: Muddy Scheme in Tcl. I am planning to implement R4RS and to add all the feactures of Arc (without continuations and with different thread model). I want to try if is possible to have one interpreter with two modes scm/arc, only changing the eval functions and special forms.
Of course It is too slow for real use, It is just a learning tool (I even had to learn how to do the mark and sweep garbage collector).
"This interpreter tries to follow the awesome "Scheme from Scratch" articles written by Peter Michaux." I learnt alot from his code too! I thought about doing some thing like "implement R4RS" eventually but figured I should learn a bit more about lisp first. I think its possible to do scm/arc together.. I'm not sure you even need to change the eval function...
