TODO

optimization: parse expression with context-awareness so that the parser can link parent nodes automatically (or at least parent abstractions)

in stepbystep mode, print arrows under terms used in reduction
    Beta reducing 'a' into '(λx. (x w))'
    (((λx. (λy. (x y))) (λw. (((λx. (x w)) a) w))) b)
                               ^^^^^^^^^^^ ^
This (i think) will require every node having a sourcelocation or something like that

generalize lexing and parsing for single word commands

write more unit tests

consider passing source to reportError function instead of keeping as instance -> will save computation in the case that there aren't any errors

possibly parse numbers into church numeral equivalent

Look into refactoring reducer and variableresolver into functional components