-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Mon, Dec 14, 2009 at 11:09:16AM -0800, Jeff Davis wrote:
[...] > I think "countable" is a more accurate word than "discrete". Strings are > discrete but not countable. Oh, no -- strings (of finite, but arbitrary length) are not discrete -- you can always squeeze one more between two given strings. In this sense there are quite similar to rational numbers. Can we call them continuous? -- it depends, it seems that the terminology here isn't consistent: sometimes the rationals are considered continuous (as per the property above mentioned), sometimes the reals (which are a much more monstrous construct!) are referred to as "the continuum". As Robert points out, they are countable; you'd need infinite length for them to be more than that (then they would behave a bit like the reals, Cantor diagonal and all that ;-) All that said, it's moot: in computers, we can't represent strings of arbitrary length (PostgreSQL has an upper limit of about 1GB, right?). The situation is even more restricted with floats (they are much smaller; thus one could say that they're more "discrete" than strings, even). Problem with floats is -- the granule is not the "same size" over the whole range (nasty), and it's all implementation-dependent (nastier). But given an implementation, the concept of "next" and "previous" on floats is (if you give me some slack with NANs) mostly well-defined. Same with strings (up-to) some fixed length. Still, it seems non-discrete is a useful abstraction? Regards - -- tomás -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFLJzqSBcgs9XrR2kYRAoydAJ9uUYt4aTj+BjuJv9XtDIU7UAAFjwCbBBSv gkw3a6oTqGOoQBHiuZjcJvQ= =l9YV -----END PGP SIGNATURE----- -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers