something akin to singleton expansion in object array assignment

Hello, I'm writing to inquire if anyone knows if it's possible to create an object array and to assign a single field many values all at once - sort of like A(1:5) = ones(1,5);. For example.

   classdef bug
      properties
         legs
      end
   end

   for i=1:5
      bugs(i) = bug();
   end

   % This doesn't work.
   bugs(1:5).legs = [6 6 8 8 4];
   % This doesn't either
   bugs.legs = [6 6 8 8 4];
   % Or this 
   bugs.legs = 6

Does one have to write a loop or maybe modify subsasgn (ugh). It seems like all other functionality available to other matlab objects is available with the built in subsasgn but this one.

Thanks in advance,

Val

Answer 1

[Walter Roberson]

Singleton expansion does not use that syntax for regular objects. Experiment with

L = num2cell([6 6 8 8 4]);
bugs(1:5).legs = L{:};

[Val Schmidt]

Thanks for the suggestion. I gave it a go and several variations on the theme. Embarrassingly, I'm missing the one that works:

   a.legs = {ones(1,5)}
   Incorrect number of right hand side elements in dot name assignment.  Missing [] around left hand side is a likely cause.

   a(:).legs  = {ones(1,5)}
   Insufficient number of outputs from function on right hand side of equal sign to satisfy overloaded assignment.

   b = num2cell(ones(1,5));
   a(1:5).legs = b{:};
   Insufficient number of outputs from function on right hand side of equal sign to satisfy overloaded assignment.

   a(1:5).legs = b(:);
   Insufficient number of outputs from function on right hand side of equal sign to satisfy overloaded assignment.

What did I miss do you think?

-Val

[Walter Roberson]

You could try

b = num2cell(ones(1,5));
a(1:5).legs = deal(b{:});

or

[a(1:5).legs] = deal(b{:});

deal() should not be necessary anymore, but it was around R2007a-ish that that changed.

Answer 2

[per isakson]

Or hide the num2cell in a function

    >> [bugs.legs] = num2list( [12 13 14 8 4] )

    bugs = 
      1x5 bug array with properties:

        legs

where

    function  varargout = num2list( num_vec )
    % num2list
        varargout = num2cell( num_vec );
    end

[Walter Roberson]

It should perhaps be

varargout(1:nargout) = num2cell( num_vec(1:nargout) );

plus of course a check in case nargout is longer than the vector.

[per isakson]

I just tried to illustrate an idea. The code works here when the length of the object array and the vector are the same. Matlab mostly requires that the length (/size) of LHS and RHS are equal(?).

Yes, one may allow the LHS to be shorter and it is possible to implement singleton expansion.

[Alfonso Nieto-Castanon]

Or even: (also without the checks)

 % num2list
 function varargout = num2list(varargout)
 end