--- a/doc/ChangeLog	Tue Apr 28 19:45:40 2009 -0400
+++ b/doc/ChangeLog	Wed Apr 29 07:44:34 2009 +0200
@@ -1,3 +1,7 @@
+2009-04-29  Jaroslav Hajek  <highegg@gmail.com>
+
+	* interpreter/numbers.txi: Update info on ranges.
+
 2009-04-26  Rik  <rdrider0-list@yahoo.com>
 	* interpreter/arith.txi: Update section 17.3 (Trigonometry) of arith.txi
 

--- a/doc/interpreter/numbers.txi	Tue Apr 28 19:45:40 2009 -0400
+++ b/doc/interpreter/numbers.txi	Wed Apr 29 07:44:34 2009 +0200
@@ -403,6 +403,25 @@
 number of elements is known, you should use the @code{linspace} function
 instead (@pxref{Special Utility Matrices}).
 
+When adding a scalar to a range, subtracting a scalar from it (or subtracting a
+range from a scalar) and multiplying by scalar, Octave will attempt to avoid
+unpacking the range and keep the result as a range, too, if it can determine
+that it is safe to do so. For instance, doing
+
+@example
+a = 2*(1:1e7) - 1;
+@end example
+
+will produce the same result as @samp{1:2:2e7-1}, but without ever forming a
+vector with ten million elements.
+
+Using zero as an increment in the colon notation, as @samp{1:0:1} is not
+allowed, because a division by zero would occur in determining the number of
+range elements. However, ranges with zero increment (i.e. all elements equal)
+are useful, especially in indexing, and Octave allows them to be constructed
+using the built-in function @dfn{ones}. Note that because a range must be a row
+vector, @samp{ones (1, 10)} produces a range, while @samp{ones (10, 1)} does not.
+
 When Octave parses a range expression, it examines the elements of the
 expression to determine whether they are all constants.  If they are, it
 replaces the range expression with a single range constant.