Re: Parsing beyond sexps

[Mattias Engdegård]

19 jan. 2020 kl. 09.11 skrev Damien Cassou <address@hidden>:

> This is not enough though as I want comments and line/column positions
> in the yielded values. Is there anything I could use from Emacs core
> that would make my life easier?

Nothing in Emacs core that I know of, but you could have a look at how the 
'relint' package does it: keep track of the position before each top-level 
form, and then maintain a path of list indices taken as it descends into each 
form. Example:

(defun select-weapon (opponent)
  "A Matter of Life and Death."
  (if (fencing-master-p opponent)
      'duelling-pistols
    'rapier))

The path to duelling-pistols would be (1 2 4), since it is built up backwards 
as a stack during descent: first take element 4 of the top-level form to the 
'if'-expression, then element 2 of that form to the (quote duelling-pistols), 
and finally element 1 to get past the quote. Maintaining the path during 
traversal turns out to be fairly cheap.

The tuple <top-level-position, path> can then be transformed into <line, 
column> (or just a buffer position) when required for diagnostics; see 
'relint--pos-line-col-from-toplevel-pos-path'. It's somewhat slow but not 
time-critical.