On Jun 1, 2006, at 21:48, web mail wrote:

> Jeff, Ezra,
>
> Thanks tons for the help. You guys both helped a lot. My only question
> so far, for Ezra, is this: My second tag is "second tag", not in  
> quotes,
> but with a space between the two words. The tag IS meant to be two  
> words
> long. So I'm thinking that if you replace all the commas with spaces,
> wont that split my second tag into two tags, when it was meant to be
> just one tag ?

You're right, that's what would happen.  The problem is that in the  
case where a non-quoted multi-word tag (second tag) occurs in the  
same input as two space-delimited single-word tags (third_tag  
fourth_tag), you're out of luck.  This isn't a problem that's  
solvable without some sort of semantic knowledge, potentially quite a  
bit of it.  For example, how would you distinguish between ("first  
tag", second tag, dog pile) and ("first tag", second tag, dog pile)  
where (dog pile) is meant as one and two tags, respectively?

> The tags can appear in any order, and they can either be quoted,
> separated by commas, or separated by spaces. I've decided that in the
> case of all three, i would like quotes to have precedence, followed by
> commas, followed by spaces. so, for an example, the following string:

I think that you're using 'precedence' in a way that's not quite  
formally correct.  Commas don't have precedence over spaces in the  
same way that * has precendence over +.  From your examples, a more  
accurate description might be: if commas occur outside of a quoted  
tag, assume that tags are comma-delimited; otherwise, assume that  
tags are space-delimited.

Even that, though, leaves you with a bit of a problem making the dog- 
pile decision, if it's the only input.  Is it meant as a single tag  
in a comma-delimited list (convention being to leave off the final  
delimiter in lists)?  Or is it meant as two tags in a space-delimited  
list?  It's still ambiguous as to what the user's intention might  
have been without delving into some sort of semantics.

Another poster (can't remember whom) interpreted your specification  
as "after the last comma, assume things are space-delimited", which  
might also be an option.

For reasons of simplicity (for the user - you're free to make your  
job as hard as you please!), though, I'd suggest that it would be  
best to stick to a single type of delimiter.  I prefer spaces,  
myself, since tags tend to be single words, and people are used to  
that sort of input (not only from the canonical examples of flickr or  
del.icio.us, but because it mimics search engines, for instance).

Matthew Smillie

[1] "Dog pile" in this sense: http://en.wikipedia.org/wiki/Pile-on  
which I thought of because, being the oldest and largest of all my  
cousins and siblings, it was always my misfortune to be on the bottom.