maybe make the repl use the readline library.
use secure functions.
make quest a thing.
remove macros?

instead of returning "#<Lambda ..." it should return the expression.
remove lambda_type and macro_type.
create lisp code for addition.
make unit testing.

split, join. (done)
make numbers be symbols. (done)
make number symbols neutral. (done)
fix a security bug of setting a primitive. (done)
improve performance of progs1. (done)
makes no sense to make progs accept a lambda argument. (because the evaluation of each step would require a fixing a symbol, such as fixing the symbol "t").
add \b interpretation. (done)
improve performance of evalProg. (done)
(random n). (done)
add math operator %. (done)
make time. (done)
makes no sense to remove numbers altogether, because symbols won't be neutral (as with previous badly thought plans).
make list structure begin with an cell which has a "special" symbol in car (still don't know which symbol might be). then make a C predicate function to detect if the car is the beginning of a list (the end already is marked by a cdr of ()). (done)
change from label to set. (done)
makefile with lib. (done)
update documentation. (done)
makes no sense to remove strings altogether. (because of " ", "(", ")", or ".")
create progs, a prog that stops if expr evaluates to n. (done)
rename progn to prog. (done)
make read function. (done)
make princ functions not print the parentesis of a list. (done)
support scripting with a shebang. (done)
receive input from stdin. (done)
make load code of argument files. (done)
remove <= , >= and = . add !. (done)
expose eval as a function. (done)
add dif. remove eq. (done)
add fill. (done)
add n. (done)