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Panu A Kalliokoski wrote:
(2) the codomain of compare functions is {-1, 0, 1} which reminds me of other (bad) programming languages where real enumerations are hard to do. While these values bear some intuitive semblance to orderings (because of the sign function), the traditional Lisp/Prolog/ML way for things like this are real descriptive values, in the case of Scheme, the symbols {less, equal, greater} (or {lt, eq, gt}). The only reason to use the nondescriptive values is AFAIU the possibility to add and multiply values produced from compare functions, which easily leads to ugly code. So, is there some kind of rationale for the codomain of compare functions?
See the section "How to represent the three cases?" in the Design Rationale: <http://srfi.schemers.org/srfi-67/srfi-67.html#node_sec_6> -- Jens Axel Søgaard