Re: [O] [RFC] Alternative to sub/superscript regexp

[Nicolas Goaziou]

Completing myself,

> OTOH, while we're at it, I wonder if we should keep grouping with
> parenthesis. I guess that if you want to use parenthesis, you're going
> to need math mode anyway, so there's no real need to make it easy to
> type, e.g. :
>
>   x^(2-i)
>
> which will become x$^\text{(2-i)}$ anyway.

I attach the suggested patch. I removed parenthesis-grouping for the
reasons I gave above. Carsten: if you'd rather keep this feature, let me
know, I'll provide another patch.

I also slightly changed the simplified regexp, as [:word:] includes
underscores in Org syntax. I used [:alnum:] instead.

Regards,

>From ffda7d038326aececd9337850d4384e4fd207459 Mon Sep 17 00:00:00 2001
From: Nicolas Goaziou <address@hidden>
Date: Wed, 18 Dec 2013 22:32:13 +0100
Subject: [PATCH] Change no brace sub/superscript syntax

* lisp/org.el (org-match-substring-regexp): Simplify syntax when not
using braces.  Also remove parenthesis as grouping characters and make
the variable a defconst.
(org-match-substring-with-braces-regexp): Make the variable a defconst
and remove a useless group in regexp.
(org-use-sub-superscripts): Update docstring.
* lisp/org-element.el (org-element-subscript-parser,
  org-element-superscript-parser): Adapt to group changes.
---
 lisp/org-element.el | 17 ++++++++---------
 lisp/org.el         | 19 +++++++------------
 2 files changed, 15 insertions(+), 21 deletions(-)

diff --git a/lisp/org-element.el b/lisp/org-element.el
index 31add7b..17062a9 100644
--- a/lisp/org-element.el
+++ b/lisp/org-element.el
@@ -3372,13 +3372,12 @@ Return a list whose CAR is `subscript' and CDR a plist 
with
 Assume point is at the underscore."
   (save-excursion
     (unless (bolp) (backward-char))
-    (let ((bracketsp (if (looking-at org-match-substring-with-braces-regexp)
-                        t
-                      (not (looking-at org-match-substring-regexp))))
+    (looking-at org-match-substring-regexp)
+    (let ((bracketsp (match-beginning 4))
          (begin (match-beginning 2))
-         (contents-begin (or (match-beginning 5)
+         (contents-begin (or (match-beginning 4)
                              (match-beginning 3)))
-         (contents-end (or (match-end 5) (match-end 3)))
+         (contents-end (or (match-end 4) (match-end 3)))
          (post-blank (progn (goto-char (match-end 0))
                             (skip-chars-forward " \t")))
          (end (point)))
@@ -3421,12 +3420,12 @@ Return a list whose CAR is `superscript' and CDR a 
plist with
 Assume point is at the caret."
   (save-excursion
     (unless (bolp) (backward-char))
-    (let ((bracketsp (if (looking-at org-match-substring-with-braces-regexp) t
-                      (not (looking-at org-match-substring-regexp))))
+    (looking-at org-match-substring-regexp)
+    (let ((bracketsp (match-beginning 4))
          (begin (match-beginning 2))
-         (contents-begin (or (match-beginning 5)
+         (contents-begin (or (match-beginning 4)
                              (match-beginning 3)))
-         (contents-end (or (match-end 5) (match-end 3)))
+         (contents-end (or (match-end 4) (match-end 3)))
          (post-blank (progn (goto-char (match-end 0))
                             (skip-chars-forward " \t")))
          (end (point)))
diff --git a/lisp/org.el b/lisp/org.el
index 59f55a8..4722714 100644
--- a/lisp/org.el
+++ b/lisp/org.el
@@ -882,7 +882,7 @@ will be parsed as single sub- or superscripts:
  10^-12  or   10^-tau    a leading sign with digits or a word
  x^2-y^3                 will be read as x^2 - y^3, because items are
                         terminated by almost any nonword/nondigit char.
- x_{i^2} or   x^(2-i)    braces or parenthesis do grouping.
+ x_{i^2}                 braces do grouping.
 
 Still, ambiguity is possible.  So when in doubt, use {} to enclose
 the sub/superscript.  If you set this variable to the symbol `{}',
@@ -5636,21 +5636,18 @@ stacked delimiters is N.  Escaping delimiters is not 
possible."
            next (concat "\\(?:" nothing left next right "\\)+" nothing)))
     (concat left "\\(" re "\\)" right)))
 
-(defvar org-match-substring-regexp
+(defconst org-match-substring-regexp
   (concat
    "\\(\\S-\\)\\([_^]\\)\\("
-   "\\(" (org-create-multibrace-regexp "{" "}" org-match-sexp-depth) "\\)"
+   "\\(?:" (org-create-multibrace-regexp "{" "}" org-match-sexp-depth) "\\)"
    "\\|"
-   "\\(" (org-create-multibrace-regexp "(" ")" org-match-sexp-depth) "\\)"
-   "\\|"
-   "\\(\\(?:\\*\\|address@hidden \t\r\n,:\"?<>~;./{}=()]+\\)\\)\\)")
+   "\\(?:\\*\\|[+-]?[[:alnum:].,\\]*[[:alnum:]]\\)\\)")
   "The regular expression matching a sub- or superscript.")
 
-(defvar org-match-substring-with-braces-regexp
+(defconst org-match-substring-with-braces-regexp
   (concat
-   "\\(\\S-\\)\\([_^]\\)\\("
-   "\\(" (org-create-multibrace-regexp "{" "}" org-match-sexp-depth) "\\)"
-   "\\)")
+   "\\(\\S-\\)\\([_^]\\)"
+   "\\(" (org-create-multibrace-regexp "{" "}" org-match-sexp-depth) "\\)")
   "The regular expression matching a sub- or superscript, forcing braces.")
 
 (defun org-make-link-regexps ()
@@ -6087,8 +6084,6 @@ by a #."
 
 (defvar org-latex-and-related-regexp nil
   "Regular expression for highlighting LaTeX, entities and sub/superscript.")
-(defvar org-match-substring-regexp)
-(defvar org-match-substring-with-braces-regexp)
 
 (defun org-compute-latex-and-related-regexp ()
   "Compute regular expression for LaTeX, entities and sub/superscript.
-- 
1.8.5.2