Scheme Request for Implementation 156, "Syntactic combiners for binary predicates," by Panicz Maciej Godek, has gone into "final" status.
The document and an archive of the discussion are available at <https://srfi.schemers.org/srfi-156/>. Here's the abstract: Recognizing binary predicates as a specific area in which the use of prefix operators is an impediment, we propose a thin layer of "syntactic stevia" for in-fixing such predicates. It can be implemented using regular Scheme macros. We suggest that the code (is x < y) should be transformed to (< x y), and (is x < y <= z) -- to (let ((y* y)) (and (< x y*) (<= y* z))). In addition, we suggest special meaning to the _ symbol: (is _ < y) and (is x < _) should be transformed to (lambda (_) (< _ y)) and (lambda (_) (< x _)), respectively. This SRFI document anlso describes some other uses of the is macro and its limitations. Note that tests are now included in the reference implementation. They can be seen in the diff from the previous draft: <https://github.com/scheme-requests-for-implementation/srfi-156/compare/031fda82658657deb73e06d017e670c9889cad47...f6ffabba1639338f091b0413422a03b18a7bae68> Regards, SRFI Editor
