0> In article <20090418122018.GB31519@parabola.demon.co.uk>, 0> Steve Ratcliffe <URL:mailto:steve@parabola.demon.co.uk> ("Steve") wrote: Steve> I like the approach using a ValueFilter which keeps the code Steve> separate and used only when needed. Steve> Steve> However, I believe that building the functionallity out of prev Steve> and subst is too low level and it would be be better to have a Steve> single filter that does everything that is necessary to add the Steve> symbol; for example ${ref|highway-symbol=box}. Steve> Steve> I say this because not all of the special values go at the Steve> beginning of the string. Some of them are used to separate Steve> the parts of a streetname (eg between 'Main' and 'Street' in Steve> "Main Street"). Also the required regular expression to fix Steve> up the ref could get complex as shown in another message in Steve> the thread. Agreed - I've been thinking about this over the weekend (too sunny to sit inside coding!) and regular expressions don't fit inline very well - after all, the pipe symbol '|' is often needed in regexps, and it's already in use in the filter syntax. I think that coding the length check into a 'highway-symbol' filter as you describe above is probably the Right Thing. I'll produce a new patch this week. What are your thoughts on the elevation prefix? Another filter, that checks for a numeric value?