From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ricardo Wurmus <rekado@elephly.net>
Subject: Re: Trouble with the PEG parser
Date: Sun, 30 Dec 2018 22:41:28 +0100
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To: swedebugia <swedebugia@riseup.net>
Cc: guix-devel <guix-devel@gnu.org>


Hi swedebugia,

It=E2=80=99s not clear to me what kind of output you=E2=80=99re expecting. =
 Let=E2=80=99s take
this example:

(define-peg-string-patterns
  "comment <- entry* !.
entry <-- (! NL .)* NL*
NL < '\n'")

This works fine, but not on your =E2=80=9C*test*=E2=80=9D string, which con=
tains the
character =E2=80=9C\(=E2=80=9D.  Note that you are in a Guile string here, =
so e.g. =E2=80=9C\n=E2=80=9D
represents the actual newline character, not a two-character string.
Your attempt to escape an opening parenthesis led to the character =E2=80=
=9C\(=E2=80=9D.

This is what the string should look like:

(define *test*
  ";; test
;;test2
; test3
;test4
(define %tor-accounts
  ;; User account and groups for Tor.")

Here=E2=80=99s what I see:

scheme@(guile-user)> (peg:tree
                      (match-pattern comment *test*))
$18 =3D ((entry ";; test") (entry ";;test2") (entry "; test3") (entry ";tes=
t4") (entry "(define %tor-accounts") (entry "  ;; User account and groups f=
or Tor."))

Is this what you expect?  It certainly is not the #F that you=E2=80=99re se=
eing.

FWIW, I suggest using s-expression patterns instead of string patterns.

--
Ricardo