Added &position START END syntax to :lambda and :destructure

[scymtym]

The change allows bodies of :lambda and :destructure transforms to receive the bounds of the matching substring in two variables. The respective syntax is:

(:lambda (ARG &position START END)
  BODY)

(:destructure (LAMBDA-LIST-ELEMENTS &position START END)
  BODY)

Modified example which includes substring bounds in parse result:

(defrule sexp (and (? whitespace) (or magic list atom))
  (:destructure (w s &position start end)
    (declare (ignore w))
    (list s (cons start end))))

[nikodemus]

I like this. Notes:

• Don't use tabs for indentation.
• &BOUNDS might be a better key than &POSITION, given that it has two arguments. &POSITION works too, though.
• I'm not sure the documentation parses right. Talking about the lambda-list accepting an additional lambda-list keyword &BOUNDS, which (1) must appear after all standard lambda list keywords (2) can be followed by variables to which bounding indexes of the matches substring are bounds might be clearer.
• Possibly move the lambda-list parsing to a separate function for clarity. DEFRULE is already big enough.

[scymtym]

Thanks for the feedback. I will update the patch accordingly.

[scymtym]

I tried to incorporate the suggested improvements.

[nikodemus]

Thanks. Can you squash those and write a single cohesive commit message, or do you want me to do that?

[scymtym]

Please do. I'm not sufficiently familiar with git yet.

[nikodemus]

Done, thanks!