Re: Custom color lexer for DrRacket that requires lookahead

> On May 30, 2016, at 11:51, Robby Findler <[email protected]> wrote:
> 
> If not, can you unpack the example a little bit more below? I don't
> get what you're saying. That, it seems like it should be okay when the
> editor contains:
> 
>  foobar
> 
> and then when the user inserts a slash to produce this:
> 
>  foo/bar
> 
> then that should continue to be okay, as the thing that calls your
> lexer will ask it to start over again at the "f" which should work, as
> long as it returns the entire "foo/bar" as a single lexeme. No?

That assessment is accurate, yes, but it doesn’t cover the common
use-case, which is typing “foo/bar” directly, not typing “foobar” then
inserting a slash within the lexeme. I type this:

  foo
     ^

where the caret represents the cursor. The colorer runs and lexes a
single symbol. Next, I type a single slash:

  foo/
      ^

Now the colorer attempts to lex the slash alone as a new token without
attempting to re-lex “foo”. Since a forward slash is not valid at the
beginning of an identifier, it is colored as an error.

Basically, when I type a forward slash, I want the preceding token to be
re-lexed. I don’t need anything more than that... just a single
character of lookahead is necessary, effectively.

(As an aside: is there any way to get the 'color-lexer property to
affect the interactions panel? It only seems to affect the definitions
panel.)

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