How to Write Seemingly Unhygieni and Referentially Opaque Ma ros with Syntax - rules

This paper details how folklore notions of hygiene and referential transparen y of R5RS ma ros are defeated by a systemati atta k. We demonstrate syntax-rules that seem to apture user identi ers and allow their own identi ers to be aptured by the losest lexi al bindings. In other words, we have written R5RS ma ros that a omplish what ommonly believed to be impossible. We build on the the fundamental te hnique by Petrofsky of extra ting variables from arguments of a ma ro. The present paper generalizes Petrofsky's idea to atta k referential transparen y. This paper also shows how to overload the lambda form. The overloaded lambda a ts as if it was infe ted by a virus, whi h propagates through the lambda's body infe ting other lambdas in turn. The virus re-de nes the ma ro being amou aged after ea h binding. This rede nition is the key insight in a hieving the overall referential opaqueness. Although we eventually subvert all binding forms, we preserve the semanti s of S heme as given in R5RS. The novel result of this paper is a demonstration that although R5RS ma ros are deliberately restri ted in expressiveness, they still wield surprising power. We have exposed faults and the la k of pre ision in ommonly held informal assertions about syntax-rule ma ros, and pointed out the need for proper formalization. For a pra ti al programmer this paper o ers an en ouragement: more and more powerful R5RS ma ros turn out to be possible.