Draft 6 says that it's an error for an argument of / (other than the first) to be an exact zero. R6RS, however, says that it's an error only if all the arguments are exact. In other words, (/ 2.0 0) is an error according to the draft, but in R6RS it returns +inf.0 (assuming the implementation supports it). The proposal is to adopt the R6RS wording.
I tested (/ 2.0 0) in the usual set of Schemes:
- Racket, Gambit, Chicken (with the numbers egg), Guile, Chibi, Elk, Spark report an error.
- Gauche, Bigloo, Scheme48/scsh, Kawa, SISC, Chez, SCM, Ikarus/Vicare, Larceny, Ypsilon, Mosh, IronScheme, NexJ, STklos, RScheme, BDC, UMB, VX return +inf.0.
- MIT, scsh, Shoe, TinyScheme, Scheme 7, XLisp, Rep, Schemik, Inlab always report an error when dividing by zero, exact or inexact.
- KSi, Scheme 9 produce incorrect results.
- SigScheme, Dream, Oaklisp, Owl Lisp don't support inexact numbers.