MATLAB: Assignment of an object to a vector

initializationobject oriented programmingvectors

Hi all and happy new year!
I have the following simple problem. I have a function say
res=myfunc(a,b,c)
  res=zeros(2,1);
  res(1)=a+log(b)+cos(c);
  res(2)=(b-c)/a;
end
in addition, I have a class say "myclass". When I call the function myfunc with numerical values for a, b and c, the result is as expected. However, when I call myfunc with inputs of class myclass, I get an error saying: "??? In an assignment A(I)=B, the number of elements in B and I must be the same"
clearly, numel(res(1)) is 1 and numel(a+log(b)+cos(c)) is also 1 although res(1) and a+log(b)+cos(c) are of different classes.
A simple workaround is to write the function above differently
res=myfunc2(a,b,c)
  res=[
  a+log(b)+cos(c)
  (b-c)/a
  ];
end
that is, rather that declaring a vector as in the first case, I construct a vector directly. In this case things work fine as well. I just don't know how to make the code work for the first case as well.
Any thoughts?
Thanks, Pat.

Best Answer

clearly, numel(res(1)) is 1 and numel(a+log(b)+cos(c)) is also 1.
That's not clear at all, since you haven't showed us how LOG, COS, and PLUS were overloaded for myclass in order to obtain the expression a+log(b)+cos(c). We have no idea based, on what you've shown, what this expression produces.
Also, MATLAB does not allow res(1) and res(2) to be of different classes. Therefore when you do
    res(1) = a+log(b)+cos(c)
MATLAB tries to convert a+log(b)+cos(c) from whatever class it is to 'double', the same class as res(2). You haven't mentioned if or how you've overloaded the double() function to accomplish this.
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