Hygienic macros through explicit renaming

This paper describes an alternative to the low-level macro facility described in the Revised4 Report on the Algorithmic Language Scheme [1]. The facility described here is based on explicit renaming of identifiers, and was developed for the first implementation of the hygienic macro expansion algorithm described in [2]. It was the first low-level macro facility to be designed for compatibility with a high-level hygienic macro system, and it remains one of the easiest to understand.