Tables: Relative row references may now cross hlines

A relative row reference like @-1 in a table may now reach across a
horizontal separator line.  I hope this will not break any important
tables out there, but I think it is the right thing to do.

The original reason for not-crossing was to implement running
averages of one column in the next.  This can now be done using field
formulas near the beginning and end of the column, and a column
formula for the central part.

See the variable `org-table-relative-ref-may-cross-hline' for more
details.

doc/org.texi

@@ -2072,9 +2072,7 @@ starts with a hline above the header, it does not count.}, @samp{II} to
 the second, etc@.  @samp{-I} refers to the first such line above the
 current line, @samp{+I} to the first such line below the current line.
 You can also write @samp{III+2} which is the second data line after the
-third hline in the table.  Relative row numbers like @samp{-3} will not
-cross hlines if the current line is too close to the hline.  Instead,
-the value directly at the hline is used.
+third hline in the table.
 
 @samp{0} refers to the current row and column.  Also, if you omit
 either the column or the row part of the reference, the current
@@ -2087,8 +2085,8 @@ Org's references with @emph{signed} numbers are floating
 references because the same reference operator can reference different
 fields depending on the field being calculated by the formula.
 
-As a special case, references like @samp{$LR5} and @samp{$LR12} can be used to
-refer in a stable way to the 5th and 12th field in the last row of the
+As a special case, references like @samp{$LR5} and @samp{$LR12} can be used
+to refer in a stable way to the 5th and 12th field in the last row of the
 table.
 
 Here are a few examples:

lisp/ChangeLog

@@ -1,3 +1,11 @@
+2009-08-01  Carsten Dominik  <carsten.dominik@gmail.com>
+
+	* org-table.el (org-table-error-on-row-ref-crossing-hline):
+	Variable made obsolete.
+	(org-table-relative-ref-may-cross-hline): New option.
+	(org-table-find-row-type): Honow the new option
+	`org-table-relative-ref-may-cross-hline'.
+
 2009-07-31  Carsten Dominik  <carsten.dominik@gmail.com>
 
 	* org-table.el (org-table-cut-region, org-table-copy-region): Work

lisp/org-table.el

@@ -247,13 +247,29 @@ Automatically means, when TAB or RET or C-c C-c are pressed in the line."
   :type 'boolean)
 
 (defcustom org-table-error-on-row-ref-crossing-hline t
-  "Non-nil means, a relative row reference that tries to cross a hline errors.
-When nil, the reference will silently be to the field just next to the hline.
-Coming from below, it will be the field below the hline, coming from
-above, it will be the field above the hline."
+  "OBSOLETE VARIABLE, please see `org-table-relative-ref-may-cross-hline'."
   :group 'org-table
   :type 'boolean)
 
+(defcustom org-table-relative-ref-may-cross-hline t
+  "Non-nil means, reltive formula references may cross hlines.
+Here are the allowed values:
+
+nil    Relative references may not cross hlines.  They will reference the
+       field next to the hline instead.  Coming from below, the reference
+       will be to the field below the hline.  Coming from above, it will be
+       to the field above.
+t      Relative references may cros hlines.
+error  An attempt to cross a hline will throw an error.
+
+It is probably good to never set this variable to nil, for the sake of
+portability of tables."
+  :group 'org-table-calculation
+  :type '(choice
+	  (const :tag "Allow to cross" t)
+	  (const :tag "Stick to hline" nil)
+	  (const :tag "Error on attempt to cross" error)))
+
 (defgroup org-table-import-export nil
   "Options concerning table import and export in Org-mode."
   :tag "Org Table Import Export"
@@ -2404,9 +2420,13 @@ and TABLE is a vector with line types."
 		  (>= i 0) (< i l)
 		  (not (eq (aref table i) type))
 		  (if (and relative (eq (aref table i) 'hline))
-		      (if org-table-error-on-row-ref-crossing-hline
-			  (error "Row descriptor %s used in line %d crosses hline" desc cline)
-			(progn (setq i (- i (if backwards -1 1)) n 1) nil))
+		      (cond
+		       ((eq org-table-relative-ref-may-cross-hline t) t)
+		       ((eq org-table-relative-ref-may-cross-hline 'error)
+			(error "Row descriptor %s used in line %d crosses hline" desc cline))
+		       (t (setq i (- i (if backwards -1 1))
+				n 1)
+			  nil))
 		    t)))
       (setq n (1- n)))
     (if (or (< i 0) (>= i l))