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Re: meta-comment on typing



bear wrote:
For example, if I know that I added something to 27 and got -32,
reversibility means I should be able to uniquely determine what was
added to 27; under the rules of linear addition, it would have to be
-59, not any positive number.  But with modular addition, it could be
either of two numbers, -59 and ($MODULUS - 59), so modular addition
isn't reversible like linear additon.

Yeah, but if you have the additional information that all "numbers" are in the range -2^31 to 2^31-1 inclusive, you can determine the unique value that was added to 27 to give -59.

I'm not saying fixnums are great, just that your example doesn't convince me that addition of fixnums is not reversible.

Regards,

Alan
--
Dr Alan Watson
Centro de Radioastronomía y Astrofísica
Universidad Astronómico Nacional de México