eopl; showcase - the PROC language
eopl; exercise 3.19 - letproc
eopl; exercise 3.20 - curried procedures
eopl; exercise 3.21 - multi-arg procedures
eopl; exercise 3.22 - unify calls and operators
eopl; exercise 3.23 - a recursive factorial
eopl; exercise 3.24 - mutual recursion w/o letrec
eopl; exercise 3.25 - the y combinator
eopl; exercise 3.26 - store smaller environments
eopl; exercise 3.27 - traceproc
eopl; exercise 3.28 - dynamic scope
eopl; exercise 3.29 - a twist on dynamic binding
eopl; showcase - the LETREC language
eopl; exercise 3.30 - why proc-val in apply-env?
eopl; exercise 3.31 - multiple args letrec
eopl; exercise 3.32 - multiple functions in letrec
eopl; exercise 3.33 - mutli-func, multi-arg letrec
eopl; exercise 3.34 - envs with procedural repr.
eopl; exercise 3.35 - self-ref extend-env-rec
eopl; exercise 3.36 - self-ref evn for mutual recursion