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K. Ari Krupnikov scripsit:
> John, the question is not "can I validate some string against *some
> criterion* because I have a tool that will?". The question is "can I
> validate some string wrt the use I intend to make of it".
No, it's "Can I cheaply and easily reduce the error rate in entered data"?
Full validation is beyond my powers, since I can't make my computer send
snail mail, still less process the replies.
> But how do you know it's *their* post code? Something tells me you are
> interested in the singleton set of *the user's* post code, not the
> larger set of *valid* post codes. Is a valid, but irrelevant, post
> code better for you than no post code at all or a bogus post code?
> 20502 is a valid US ZIP code. Do you want to send mail there that is
> addressed to me?
If you enter that, it's your problem. But if you mean to type 10003 and
type 1003, I will not accept that (given country=US).
> Whose money you take is up to you. But after you take their money, you
> want to know where they are, don't you (although I'm not sure why)?
Partly because I get a cheaper rate from a credit card processor if the
address I supply matches the one associated with the card.
In addition, users don't get access without a signed contract, and I need
somewhere to tell Sales to send it.
> Presumably, you give your users a drop-down list and not a text field
> to reduce data-entry errors. As the list of enumerations grows longer,
> it becomes a greater potential source of errors than an unconstrained
> string because users can't be bothered to read through its entire
A valid point. If more people knew their ISO 3166 country code, I would
allow them to type that and validate it on the fly.
> Validation, wither regexp- or set-based, only catches so many errors,
> while giving you the illusion that your data are somehow
No, while giving me the assurance that my data is not incorrect in easily
checkable ways. It does not refer to a non-existent country (though it
could refer to the wrong country); it does not refer to an impossible
zip code (though it could refer to an unused or incorrect one).
John Cowan http://www.ccil.org/~cowan email@example.com
Please leave your values | Check your assumptions. In fact,
at the front desk. | check your assumptions at the door.
--sign in Paris hotel | --Cordelia Vorkosigan