[mkgmap-dev] Re: Code for Highway Symbols

Mon Apr 20 12:08:09 BST 2009

0> In article <20090418122018.GB31519 at parabola.demon.co.uk>,
0> Steve Ratcliffe <URL:mailto:steve at 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?