On 17 Mar 2008, at 21:58, Gunnar Hjalmarsson wrote:
In this case, if I understand it correctly, the default version of
the page, with a form, would appear. Why would that be a problem for
anybody but the stupid user? ;-)
Fundamentally, don't make it possible for your users to do anything to
surprise you.
It would have been a benign surprise this time, once these bad habits
become entrenched it will only be a matter of time before you get a
nasty surprise.
Case in point:
I once wrote some indexing code, things being what they were I had to
make fairly efficient use of disk space. I decided on a simple bit-
packing scheme, so each byte could flag the existence of a word in up
to 8 objects. With sparse files, this was quite efficient indeed.
Somewhere in the code I had a check like this:
if (! $index_byte ) {
[ code to process the next byte ]
}
else {
[ process this byte ]
}
Seems pretty bulletproof doesn't it? If the index byte is empty then
we skip on to the next byte, as we don't have any entries at all for
those 8 objects.
Testing showed a problem.... occasionally index entries were missing.
A lot of digging found the culprit.... if you have a scalar byte
holding 8 bits worth of data, it's not just when it holds 0x00 that
that test is true - it's also when it holds 0x30 - ascii '0'.
ALWAYS make your tests as specific as possible, and care about the
exceptions.
- Justin
--
Justin Hawkins
[EMAIL PROTECTED]
http://hawkins.id.au/~justin/
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