lly if you can write them
in a language like Scheme that gives you garbage collection and
closures for free.  

<p> The restriction that the compiler had to be
correct both in R5RS Scheme and in the language that it could compile
was really a pain.  For example, although I could add new syntactic
forms to the language that it could compile, and I could add new
syntactic forms with R5RS macro definitions, I couldn't simplify the
compiler by adding new syntactic forms, because the compiler can't
compile R5RS 