The final feature to cover in order to have a complete enough language to build a standard library on is macros. Write Yourself A Scheme unfortunately does not cover how to implement this, but it gives some pointers in the conclusion:
"Basically, you'd want to intersperse a function between readExpr and eval that takes a form and a macro environment, looks for transformer keywords, and then transforms them according to the rules of the pattern language, rewriting variables as necessary."
The final feature to cover in order to have a complete enough language to build a standard library on is macros. Write Yourself A Scheme unfortunately does not cover how to implement this, but it gives some pointers in the conclusion:
"Basically, you'd want to intersperse a function between readExpr and eval that takes a form and a macro environment, looks for transformer keywords, and then transforms them according to the rules of the pattern language, rewriting variables as necessary."