[Mapcss] Regexp as attribute selection

[Richard Fairhurst]

Chris Browet wrote:
> In the doc, it is described that regexp attribute selection is allowed
> ("way[highway=~/primary/]    /* regex */").
>
> While it is inherently nice, the problem is that there is almost as many
> regexp syntaxes as there are implementations.
> At least, the syntax used should be defined (is the example perl?) but I
> doubt it will be practical to implement a specific syntax for MapCSS in
> every programming language (not even speaking of those not having
> builtin support).
>
> Shouldn't it be wise to remove this from the spec and replace it by
> simpler cardinals ('*', '?' and maybe others)?

I'd strongly like to stick with regexes.

They are built into many languages and available as a library for 
others. If we require people to build their own pattern matchers, that 
will make it harder for people to implement MapCSS parsers.

PCRE is a widely-used regex standard which we could recommend. Any 
differences are usually reasonably trivial and esoteric (for example, 
http://www.mail-archive.com/develop@xcruciate.co.uk/msg00031.html only 
lists two edge cases in which PCRE differs from JavaScript/ECMAScript).

Wikipedia suggests this will give us widespread compatibility: "Java, 
JavaScript, PCRE, Python, Ruby, Microsoft's .NET Framework, and the 
W3C's XML Schema all use regular expression syntax similar to Perl's. 
Some languages and tools such as Boost and PHP support multiple regular 
expression flavors".

cheers
Richard