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Re: [Scheme-reports] Numerical example (real? -2.5+0.0i)
Aubrey Jaffer scripsit:
> | > That's reasonable: in fact, SCM doesn't support exact/exact
> | > complex numbers either, which is perfectly fine. It just means
> | > that no general complex number can be real.
> All real numbers are complex numbers. This derives from their
> mathematical definitions.
*General* complex number is a term defined in R5RS: it means non-real
complex number, where "general" is used in the sense of "general case."
Because it seems to confuse people, I have removed it from the draft R7RS.
> Shouldn't the predicates REAL? and COMPLEX? implement the mathematical
> semantics for which they are named?
Inexact numbers don't obey mathematical semantics in any case: for
example, inexact addition is not associative. There are two reasonable
sets of semantics here, and by providing two sets of procedures we
can support both. By adding an "exact-complex" feature, a program
that depends on exact complex numbers can rely on being run only on an
implementation that supports them.
Almost all theorems are true, John Cowan <cowan@x>
but almost all proofs have bugs. http://www.ccil.org/~cowan
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