# HG changeset patch
# User dbateman
# Date 1177619011 0
# Node ID 00fad3bad2a50ddc55695d706491ed62617a0f5f
# Parent  e4ea529efab083dc9d1f1dcf0d77c9f0f3c7d7a3
[project @ 2007-04-26 20:23:31 by dbateman]

diff --git a/doc/ChangeLog b/doc/ChangeLog
--- a/doc/ChangeLog
+++ b/doc/ChangeLog
@@ -1,3 +1,8 @@
+2007-04-26  David Bateman  <dbateman@free.fr>
+
+	* interpreter/stmt.txi: Document for loops over matrices, arrays
+	and cell arrays.
+
 2007-04-25  David Bateman  <dbateman@free.fr>
 
 	* interpreter/dynamic.txi: Add additional copyrights. Add sections
diff --git a/doc/interpreter/stmt.txi b/doc/interpreter/stmt.txi
--- a/doc/interpreter/stmt.txi
+++ b/doc/interpreter/stmt.txi
@@ -506,6 +506,44 @@
 loop body is executed again.  This process continues until there are no
 more elements to assign.
 
+Within Octave is it also possible to iterate over matrices or cell arrays
+using the @code{for} statement. For example consider
+
+@example
+@group
+disp("Loop over a matrix")
+for i = [1,3;2,4]
+  i
+endfor
+disp("Loop over a cell array")
+for i = @{1,"two";"three",4@}
+  i
+endfor
+@end group 
+@end example
+
+@noindent
+In this case the variable @code{i} takes on the value of the columns of
+the matrix or cell matrix. So the first loop iterates twice, producing
+two column vectors @code{[1;2]}, follwed by @code{[3;4]}, and likewise
+for the loop over the cell array. This can be extended to loops over
+multidimensional arrays. For example
+
+@example
+@group
+a = [1,3;2,4]; b = cat(3, a, 2*a);
+for i = c
+  i
+endfor
+@end group 
+@end example
+
+@noindent
+In the above case, the mulitdimensional matrix @var{c} is reshaped to a
+two dimensional matrix as @code{reshape (c, rows(c),
+prod(size(c)(2:end)))} and then the same behavior as a loop over a two
+dimensional matrix is produced.
+
 Although it is possible to rewrite all @code{for} loops as @code{while}
 loops, the Octave language has both statements because often a
 @code{for} loop is both less work to type and more natural to think of.
diff --git a/src/ChangeLog b/src/ChangeLog
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2007-04-26  David Bateman  <dbateman@free.fr>
+
+	* pt-loop.cc (tree_simple_for_command::eval (void)): Correct
+	reshaping of dim_vector in for loop for multi-dimensional array.
+
 2007-04-26  John W. Eaton  <jwe@octave.org>
 
 	* load-save.cc (find_file_to_load): Only consider regular files.
diff --git a/src/pt-loop.cc b/src/pt-loop.cc
--- a/src/pt-loop.cc
+++ b/src/pt-loop.cc
@@ -403,6 +403,7 @@
 	int ndims = dv.length ();
 	for (int i = 2; i < ndims; i++)
 	  dv(1) *= dv(i);
+	dv.resize (2);
 
 	if (dv(1) > 0)
 	  {
@@ -455,6 +456,7 @@
 	int ndims = dv.length ();
 	for (int i = 2; i < ndims; i++)
 	  dv(1) *= dv(i);
+	dv.resize (2);
 
 	if (dv(1) > 0)
 	  {
diff --git a/test/ChangeLog b/test/ChangeLog
--- a/test/ChangeLog
+++ b/test/ChangeLog
@@ -1,3 +1,8 @@
+2007-04-26  David Bateman  <dbateman@free.fr>
+
+	* test_for.m: Add tests for multi-dimensional matrices and cell
+	arrays.
+
 2007-04-04  Rafael Laboissiere  <rafael@debian.org>
 
 	* Makefile.in (clean): Also remove a.wav file created by
diff --git a/test/test_for.m b/test/test_for.m
--- a/test/test_for.m
+++ b/test/test_for.m
@@ -80,3 +80,16 @@
 %! printf_assert ("\n");
 %! assert(prog_output_assert("34"));
 
+%!test
+%! a = [1,3;2,4];
+%! j = 0;
+%! for i = cat (3, a, 4 + a)
+%!   assert (i, [1;2] + 2*j++)
+%! endfor
+
+%!test
+%! a = {1,3;2,4};
+%! j=0
+%! for i = cat (3, a, cellfun(@(x) 4 + x, a, 'UniformOutput', 0))
+%!   assert (i, {1 + 2*j; 2 + 2*j++})
+%! endfor