status: final (2017-12-18)See also SRFI 26: Notation for Specializing Parameters without Currying.
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)
(let ((y* y)) (and (< x y*) (<= y* z))).
In addition, we suggest special meaning to the
(is _ < y) and
(is x < _)
should be transformed to
(lambda (_) (< _ y))
(lambda (_) (< x _)), respectively.
This SRFI document also describes some other uses of the
is macro and its limitations.