Dear Arthur,

The version of van Tonder’s macro expander included in the SRFI 72 repository is not the correct one.

After publishing SRFI 72, van Tonder came out with a version meant to conform to the (older) psyntax-style semantics chosen by R6RS, which SRFI 72 explicitly criticizes (rightly or wrongly). The version in the repo is the later R6RS-style one.

In practice, since R6RS decided on Dybvig’s ‘original’ syntax-case semantics, probably nobody will want to run the ‘correct’ version of SRFI 72 any more. But SRFI sample implementations should reflect their text as a matter of principle; and van Tonder’s original specification is of historical interest, as well as of interest to those who might want to implement hygienic macros in other languages than Scheme, who might prefer van Tonder’s semantics.

The correct versions are in the Internet Archive here, predating SRFI 93: <https://web.archive.org/web/20060823223350/http://www.het.brown.edu/people/andre/macros/implementation/>

Best wishes

Daphne