Hi Stefano,
I've tested it: it does not work.
Neither in edit nor in list view the HTML encoded characters show correctly.
Only in the "Quick filter" menu they show as they should!
But then selecting them in the quick filter will not find any entries :-(

So the short answer: 
avoid characters with a special meaning for regular-expressions in attribute values, in particular if you want to use quick filters.

Cheers
Andreas

> Hi Stefano,
> you could try to html encode the "+" and "-" sign in the option list
> Options Half = +x, -x, both
> Allow HTML = 1
> 
> But of course then you would need to change all existing entries.
> 
> It is just an idea; I did not try this out, it might not work anyway.
> 
> Cheers
> Andreas
> 
> > Dear experts,
> >    I have an elog with an attribute with fixed values, like this:
> > 
> > Attributes = Half
> > Options Half = +x, -x, both
> > 
> > It works fine, but I would like to find (or quick filter) all entries with Half=+x .
> > 
> > If I go to the search form, I can select +x from the dropdown menu for Half, but the search returns no result, even if I do have a number of entries with Half=+x. Likewise if I try to do the same with Quick filter.
> > 
> > I believe that this is due to the fact that the search uses regex, and "+" is reserved. I've tried to perform a search by entering manually and escaped "\+x", and it works as intended.
> > 
> > https://.../?mode=summary&reverse=0&reverse=1&npp=20&Half=%5E%5C%2Bx%24
> > 
> > However, since this attribute has a list of fixed values, it is not possible to entry manually something different "\+x" than what is defined in the config, that is "+x".
> > 
> > Is there a solution for this problem?
> > 
> > I would rather not change the attributes options (to, say, positive/negative), since that would mean changing manually a non negligible number of entries.
> > 
> > thanks,
> >   Stefano