Fix ses-delete-blanks to delete only blanks + documentation.

* doc/misc/ses.texi (Quick Tutorial): Mention the '!'
'ses-range' modifier as an alternative to 'ses+'.
(Advanced Features): Add a refernce to node 'Nonrelocatable
references' concerning function 'ses-rename-cell'.
(Standard formula functions): Mention the '!' 'ses-range'
modifier as an alternative to 'ses-delete-blanks'.
(More on cell printing): Fix fallback printer
definition.  Minor editorial formatting changes.
(Nonrelocatable references): Document the use of
'ses-rename-cell' as a better way to make cell reference
non-relocatable.
(The data area): Document the presence of local printer
definitions in the data area.

* lisp/ses.el (ses-delete-blanks): Do not remove
*error*.  Any error in an argument should propagate into the
using formula rather than being silently hidden !

doc/misc/ses.texi

@@ -187,6 +187,14 @@ the end-points, e.g.:
 (The @code{apply} is necessary because @code{ses-range} produces a
 @emph{list} of values. This allows for more complex possibilities.)
 
+Alternatively you can use the @code{!} modifier of @code{ses-range} to
+remove blank cells which allows to use @code{+} instead of
+@code{ses+}:
+
+@lisp
+(apply '+ (ses-range A2 A5 !))
+@end lisp
+
 @c ===================================================================
 
 @node The Basics
@@ -595,8 +603,8 @@ Pops up a menu to set the current row as the header, or revert to
 column letters.
 @item M-x ses-rename-cell
 @findex ses-rename-cell
-Rename a cell from a standard A1-like name to any
-string.
+Rename a cell from a standard A1-like name to any string that can be a
+valid local variable name (See also @ref{Nonrelocatable references}).
 @item M-x ses-repair-cell-reference-all
 @findex ses-repair-cell-reference-all
 When you interrupt a cell formula update by clicking @kbd{C-g}, then
@@ -791,8 +799,17 @@ are some useful functions to call from your formulas:
 
 @table @code
 @item (ses-delete-blanks &rest @var{args})
-Returns a list from which all blank cells (value is either @code{nil} or
-'*skip*) have been deleted.
+Returns a list from which all blank cells (value is either @code{nil}
+or '*skip*) have been deleted. Order of args is reverted. Please note
+that @code{ses-range} has a @code{!} modifier that allows to remove
+blanks, so it is possible to write:
+@lisp
+(ses-range A1 A5 !)
+@end lisp
+instead of
+@lisp
+(apply 'ses-delete-blanks (ses-range A1 A5 <))
+@end lisp
 
 @item (ses+ &rest @var{args})
 Sum of non-blank arguments.
@@ -842,9 +859,9 @@ this to undo the effect of @kbd{t}.
 @end table
 
 When a printer function signals an error, the fallback printer
-@samp{"%s"} is substituted. This is useful when your column printer
+@samp{"%S"} is substituted. This is useful when your column printer
 is numeric-only and you use a string as a cell value. Note that the
-standard default printer is ``%.7g'' which is numeric-only, so cells
+standard default printer is @samp{"%.7g"} which is numeric-only, so cells
 that are empty of contain strings will use the fallback printer.
 @kbd{c} on such cells will display ``Format specifier doesn't match
 argument type''.
@@ -986,15 +1003,27 @@ can type ahead without worrying about the glitch.
 @kbd{C-u C-y} relocates none of the cell-references. What about mixed
 cases?
 
-You can use
+The best way is to rename cells that you do not want to be relocatable
+by using @code{ses-rename-cell}.
+@findex ses-rename-cell
+Cells that do not have an A1-like name style are not relocated on
+yank. Using this method, the concerned cells won't be relocated
+whatever formula they appear in. Please note however that when a
+formula contains some range @code{(ses-range @var{cell1} @var{cell2})}
+then in the yanked formula each range bound @var{cell1} and
+@var{cell2} are relocated, or not, indepently, depending on whether
+they are A1-like or renamed.
+
+An alternative method is to use
 @lisp
 (symbol-value 'B3)
 @end lisp
 to make an @dfn{absolute reference}. The formula relocator skips over
 quoted things, so this will not be relocated when pasted or when
 rows/columns are inserted/deleted. However, B3 will not be recorded
 as a dependency of this cell, so this cell will not be updated
-automatically when B3 is changed.
+automatically when B3 is changed, this is why using
+@code{ses-rename-cell} is most of the time preferable.
 
 The variables @code{row} and @code{col} are dynamically bound while a
 cell formula is being evaluated. You can use
@@ -1011,12 +1040,13 @@ kind of dependency is also not recorded.
 @findex ses-reconstruct-all
 
 Begins with an 014 character, followed by sets of cell-definition
-macros for each row, followed by column-widths, column-printers,
+macros for each row, followed by the set of local printer
+defintitions, followed by column-widths, column-printers,
 default-printer, and header-row. Then there's the global parameters
-(file-format ID, numrows, numcols) and the local variables (specifying
-@acronym{SES} mode for the buffer, etc.).
+(file-format ID, row count, column count, local printer count) and the
+local variables (specifying @acronym{SES} mode for the buffer, etc.).
 
-When a @acronym{SES} file is loaded, first the numrows and numcols values are
+When a @acronym{SES} file is loaded, first the global parameters are
 loaded, then the entire data area is @code{eval}ed, and finally the local
 variables are processed.
 

lisp/ses.el

@@ -1,3 +1,4 @@
+
 ;;; ses.el -- Simple Emacs Spreadsheet -*- lexical-binding:t -*-
 
 ;; Copyright (C) 2002-2016 Free Software Foundation, Inc.
@@ -3746,7 +3747,7 @@ Use `math-format-value' as a printer for Calc objects."
  "Return ARGS reversed, with the blank elements (nil and *skip*) removed."
  (let (result)
  (dolist (cur args)
- (unless (memq cur '(nil *skip* *error*))
+ (unless (memq cur '(nil *skip*))
  (push cur result)))
  result))