FIND? behavior

[thomp]

Thanks for making your parser combinator code available. Fun stuff. I noted that FIND?, while advertised as looking for the first match, does not seem to leave the context at the corresponding point (i.e., directly succeeding the first match):

PARSER-COMBINATORS>  (tree-of (current-result 
                   (parse-string 
                (mdo (<- x (find? "aa"))
                     (<- c (context?))
                 (result (cons x (context-peek c))))
            "aabbaacc")))
("aa" . #\c)

Given the advertised behavior of FIND?, would it be preferable to leave the context at the point directly after the first match?

PARSER-COMBINATORS>  (tree-of (current-result 
               (parse-string 
            (mdo (<- x (find?2 "aa"))
                 (<- c (context?))
                 (result (cons x (context-peek c))))
            "aabbaacc")))
("aa" . #\b)

where FIND?2 is something like

(defun find?2 (q)
  (with-parsers (q)
    (mdo (<- x (breadth? q nil nil))
     (result (first x)))))

Thanks again,

Alan

[Ramarren]

The actual problem was in breadth? parser, which didn't emit an empty match even when argument MIN was nil/0, which means that FIND? only matched when there was at least one other token before the match. I fixed that (by removing a condition actually, not sure what I was thinking) and added a test case.

FIND? doesn't technically always find the first match, since backtracking might force a match to another one. FIND* actually forces the first match. I clarified the docstrings.

[thomp]

Looks good to me.