Re: Custom color lexer for DrRacket that requires lookahead

> On May 30, 2016, at 12:23, Alexis King <[email protected]> wrote:
> 
> 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.

Actually, I realized just after sending this that my description is not
the full picture. I think the confusion probably stems from that the
colorer does, in fact attempt to re-lex “foo” once the forward slash is
typed. However, since a trailing slash is illegal at the end of an
identifier as well, it’s still lexed as an error. Now, I keep typing:

  foo/bar
	 ^

This presumably causes the slash to be re-lexed, but since it’s still
illegal at the beginning of a token, the lexer still fails. My guess
here was that I needed to include a backup-distance on the error token,
but that doesn’t seem to help, so I’m unsure how to properly indicate
the need to re-lex the entire “foo/bar” token once “bar” is added.

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