Re: [RFC] The "c" Org macro

[Nicolas Goaziou <mail@nicolasgoaziou.fr>]

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Hello,

Eric S Fraga <e.fraga@ucl.ac.uk> writes:

> On Monday,  8 May 2017 at 15:32, Dushyant Juneja wrote:
>> A very useful macro indeed!
>>
>> One suggestion: can this also be made to support nested headings. For instance:
>> * Part {{{c}}}
>> ** Part {{{c}}}.{{{c}}}
>> * Part {{{c}}}
>
> I think this is what separate counters will enable but also motivates
> need to be able to reset a counter (e.g. the sub-heading one in above
> example if it were to be used in the second part).

Good idea.

Here is an updated patch, in which one can write

  {{{c(sub,reset)}}}
  {{{c(sub, 5)}}}

or even, for the default macro

 {{{c(,reset)}}}
 {{{c(, 99)}}}

I find the manual entry a bit awkward. Suggestions welcome.

Regards,

-- 
Nicolas Goaziou

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From 31397ffa1b0bf9795e2bc11568598af13db6c609 Mon Sep 17 00:00:00 2001
From: Nicolas Goaziou <mail@nicolasgoaziou.fr>
Date: Mon, 8 May 2017 12:38:38 +0200
Subject: [PATCH] org-macro: Implement the "c" macro

* lisp/org-macro.el (org-macro--counter-table): New variable.
(org-macro--counter-initialize):
(org-macro--counter-increment): New functions.
(org-macro-initialize-templates): Use new functions.

* doc/org.texi (Macro replacement): Document new macro.
---
 doc/org.texi      | 10 ++++++++++
 lisp/org-macro.el | 38 +++++++++++++++++++++++++++++++++++---
 2 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/doc/org.texi b/doc/org.texi
index 312870f91..6072fcb78 100644
--- a/doc/org.texi
+++ b/doc/org.texi
@@ -10852,6 +10852,16 @@ This macro refers to the filename of the exported file, if any.
 This macro returns the value of property @var{PROPERTY-NAME} in current
 entry.  If @var{SEARCH-OPTION} (@pxref{Search options}) refers to a remote
 entry, it will be used instead.
+
+@item @{@{@{c@}@}@}
+@itemx @{@{@{c(@var{NAME})@}@}@}
+@itemx @{@{@{c(@var{NAME},@var{RESET})@}@}@}
+@cindex c, macro
+@cindex counter, macro
+This macro returns the number of occurrences of this macro expanded so far.
+You can use more than one counter using different @var{NAME} values.  If
+@var{RESET} is non-empty, the specified counter is reset to the value
+specified if it is a number, or 1 otherwise.
 @end table
 
 The surrounding brackets can be made invisible by setting
diff --git a/lisp/org-macro.el b/lisp/org-macro.el
index 71e917b71..afd302932 100644
--- a/lisp/org-macro.el
+++ b/lisp/org-macro.el
@@ -36,8 +36,11 @@
 
 ;; Along with macros defined through #+MACRO: keyword, default
 ;; templates include the following hard-coded macros:
-;; {{{time(format-string)}}}, {{{property(node-property)}}},
-;; {{{input-file}}} and {{{modification-time(format-string)}}}.
+;;   {{{time(format-string)}}},
+;;   {{{property(node-property)}}},
+;;   {{{input-file}}},
+;;   {{{modification-time(format-string)}}},
+;;   {{{c(counter,reset}}}.
 
 ;; Upon exporting, "ox.el" will also provide {{{author}}}, {{{date}}},
 ;; {{{email}}} and {{{title}}} macros.
@@ -129,7 +132,7 @@ function installs the following ones: \"property\",
 	    (let ((old-template (assoc (car cell) templates)))
 	      (if old-template (setcdr old-template (cdr cell))
 		(push cell templates))))))
-    ;; Install hard-coded macros.
+    ;; Install "property", "time" macros.
     (mapc update-templates
 	  (list (cons "property"
 		      "(eval (save-excursion
@@ -143,6 +146,7 @@ function installs the following ones: \"property\",
                       l)))))
         (org-entry-get nil \"$1\" 'selective)))")
 		(cons "time" "(eval (format-time-string \"$1\"))")))
+    ;; Install "input-file", "modification-time" macros.
     (let ((visited-file (buffer-file-name (buffer-base-buffer))))
       (when (and visited-file (file-exists-p visited-file))
 	(mapc update-templates
@@ -152,6 +156,10 @@ function installs the following ones: \"property\",
 				  (prin1-to-string visited-file)
 				  (prin1-to-string
 				   (nth 5 (file-attributes visited-file)))))))))
+    ;; Initialize and install "c" macro.
+    (org-macro--counter-initialize)
+    (funcall update-templates
+	     (cons "c" "(eval (org-macro--counter-increment \"$1\" \"$2\"))"))
     (setq org-macro-templates templates)))
 
 (defun org-macro-expand (macro templates)
@@ -280,6 +288,9 @@ Return a list of arguments, as strings.  This is the opposite of
     s nil t)
    "\000"))
 
+\f
+;;; Helper functions and variables for internal macros
+
 (defun org-macro--vc-modified-time (file)
   (save-window-excursion
     (when (vc-backend file)
@@ -304,6 +315,27 @@ Return a list of arguments, as strings.  This is the opposite of
 	  (kill-buffer buf))
 	date))))
 
+(defvar org-macro--counter-table nil
+  "Hash table containing counter value per name.")
+
+(defun org-macro--counter-initialize ()
+  "Initialize `org-macro--counter-table'."
+  (setq org-macro--counter-table (make-hash-table :test #'equal)))
+
+(defun org-macro--counter-increment (name &optional reset)
+  "Increment counter NAME.
+NAME is a string identifying the counter.  If optional argument
+RESET is a non-empty string, reset the counter instead."
+  (if (org-string-nw-p reset)
+      (let ((new-value (if (string-match-p "\\`[ \t]*[0-9]+[ \t]*\\'" reset)
+			   (string-to-number reset)
+			 1)))
+	(puthash name new-value org-macro--counter-table))
+    (let ((value (gethash name org-macro--counter-table)))
+      (puthash name
+	       (if (null value) 1 (1+ value))
+	       org-macro--counter-table))))
+
 
 (provide 'org-macro)
 ;;; org-macro.el ends here
-- 
2.12.2