Per Bothner scripsit:
It never has been. If you look at R6RS, you'll see that these predicates
> What should be the result of (infinite? +nan.0+inf.0i)? The report
> says #t but that seems undesirable, because it would mean that
> finite?/infinite?/nan? would no longer be a partitioning of the
> complex numbers,
are defined on real numbers only; the extension to complex numbers is
new in R7RS. The WG decided that the convention that a partly-infinite
complex number is an infinity and that a partly-NaN complex number is
a NaN was more important than extending the trichotomy.
There was some sentiment for declaring that any complex operation
that generated a partial NaN should generate a NaN, pure and simple,
but there were strong objections from the users of complex numbers,
who expected to be able to extract meaningful results from a partial NaN.
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