Hello,

the SRFI defines: "The hash function takes an object and returns an
exact non-negative integer."

Then gives this example:
"(make-comparator real? = < (lambda (x) (exact (abs x)))) will return
a comparator expressing the natural ordering of real numbers and a
plausible (but not optimal) hash function."

This hash function however for most reals will not return an integer.

HTH