How to output matrix dimensions together with its content?

Question

Is it possible to make GNU Octave to output matrix dimensions together with its content? For example, it should produce smth. like this:

octave:1> X = [1 2; 3 4]

X [2x2] =

   1   2
   3   4


octave:2> X(1,:)

ans [1x2] =

   1   2

Answer 1

In MATLAB, create display.m in a folder called @double somewhere in your path with this content:

function display(v)
name = inputname(1);
if isempty(name)
    name = 'ans';
end
s = num2cell(size(v));
fprintf('\n%s [%d%s] =\n\n', name, s{1}, sprintf('x%d', s{2:end}));
builtin('disp', v);
end

This way you override the display method for class double, and get exactly what you have described. However, this will not work for other classes like int8, logical or cell. You have to override the method for all classes you are interested in. Example:

>> A=ones(2,2,2)

A [2x2x2] =

(:,:,1) =
     1     1
     1     1
(:,:,2) =
     1     1
     1     1

Answer 2

While Mohsen's answer does the job indeed, I felt that a separate m-file is somewhat an overkill for this purpose (especially if you don't want to clutter your directory with additional m-files). I suggest using a local anonymous function one-liner instead (let's name it dispf), so here are its evolution phases :)

The basic anonymous function I came up with is:

dispf = @(x)fprintf('%s =\n\n%s\n', inputname(1), disp(x));

which is essentially equivalent to the output in the command window after entering statements (that do not end with a semicolon, of course). Well, almost... because if inputname returns an empty string, it doesn't print 'ans' (and it should). But this can be corrected:

dispf = @(x)fprintf('%s=\n\n%s\n', ...
    regexprep([inputname(1), ' '], '^ $', 'ans '), ...
    disp(x));

This is basically using regexprep to match an empty string and replace it with 'ans'. Finally, we append the dimensions after the variable name:

dispf = @(x)fprintf('%s%s =\n\n%s\n', ...
    regexprep([inputname(1), ' '], '^ $', 'ans '), ...
    strrep(mat2str(size(x)), ' ', 'x'), ...
    disp(x));

Now you can plug this one-liner is into any script without the need for an additional m-file!

Example

Just a proof that it's working:

dispf = @(x)fprintf('%s%s =\n\n%s\n', ...
    regexprep([inputname(1), ' '], '^ $', 'ans '), ...
    strrep(mat2str(size(x)), ' ', 'x'), ...
    disp(x));

A = [1 2; 3 4];
dispf(A)
dispf(A(1, :))

The result is as expected:

A [2x2] =

   1   2
   3   4

ans [1x2] =

   1   2