allow #:command-char argument to scribble lexer

[mflatt]

@robby: Do I remember correctly that DrRacket's syntax colorer will call scribble-lexer multiple times, so that the regular expressions here would be compiled multiple times with the additional argument? If so, I think it makes sense to add a make-scribble-lexerlayer, where scribble-lexer is the result of calling that function with #\@, and so on.

[rfindler]

Yes, I believe so. And I agree that currying is a good approach.

[AlexKnauth]

Ok, I changed it to use the currying approach with make-scribble-lexer and make-scribble-inside-lexer.

[mflatt]

Bumped version, added tests, added docs, and merged. As it turns out, my first test was to use #+ as the character, which broke some of the regexp constructions. I adjusted those constructions.

[AlexKnauth]

Oh, I hadn't thought of that. But shouldn't it use regexp-quote instead to do that?

[AlexKnauth]

Otherwise won't it break for \ and ^ for example? (and probably others I haven't thought of yet)

[mflatt]

I didn't think to try those; \ seems to work and ^ fails. More tests and repairs would be welcome!

[mflatt]

I didn't use regexp-quote because I thought that it would be more complicated than dropping characters into "[...]", but I think I chose badly.