In article <[EMAIL PROTECTED]>, Steve Holden <[EMAIL PROTECTED]> wrote:
> Roy Smith wrote: > > Boris Borcic <[EMAIL PROTECTED]> wrote: > >> Complex numbers are like a subclass of real numbers > > > > I wouldn't use the term "subclass". It certainly doesn't apply in the same > > sense it applies in OOPLs. For example, you can't say, "All complex > > numbers are real numbers". In fact, just the opposite. > > > > But, it's equally wrong to say, "real numbers are a subclass of complex > > numbers", at least not if you believe in LSP > > (http://en.wikipedia.org/wiki/Liskov_substitution_principle). For example, > > it is true that you can take the square root of all complex numbers. It is > > not, however, true that you can take square root of all real numbers. > > > That's not true. I suspect what you are attempting to say is that the > complex numbers are closed with respect to the square root operation, > but the reals aren't. Yes, that's what I was trying to say. > I don't think "subclass" has a generally defined meaning in mathematics That may be true, but this is a programming newsgroup, so I was using a programming sort of definition. -- http://mail.python.org/mailman/listinfo/python-list
