MATLAB Answers

Variable size class properties for C++ code export

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Torsten Knüppel
Torsten Knüppel on 10 Jul 2019
Commented: Viet Nguyen on 10 Mar 2020
Dear all,
I would like to use a class as input to a function that is later exported to C++-code.
Something like:
classdef inputClass
properties
var(:, 1)
b = 0
end
end
Here var(:, 1) means, that I want var to be of variable size. However, as soon as I use var the coder complains about mismatching sizes, stating that var is of size 0x1. Can I somehow declare a class property to be of variable size? According to the page here, coder.varsize does not work.
Thanks in advance
Torsten

  3 Comments

Guillaume
Guillaume on 10 Jul 2019
I don't know much about coder (don't have the toolbox), but reading the page you link, I'm not sure that you can have variable size class properties. However, that page is really lacking in details.
In any case, you certainly don't have to specify the (:, 1) since I doubt that coder generates the required property validation code anyway.
rotton
rotton on 14 Aug 2019
Which Matlab version are you on? I don't have Coder either, but this reminds me very much of a problem I had some time ago, which turned out to be a bug! This was in R2017b, so it should be fixed by now. Read here for details.
Viet Nguyen
Viet Nguyen on 10 Mar 2020
Did you end up getting this resolved? I am running into the same error.

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Answers (1)

Sayyed Ahmad
Sayyed Ahmad on 10 Jul 2019
The defination of var is wrong.
it's ok if you write
classdef inputClass
properties
var;
b = 0
end
methods
function o = inputClass(varargin)
if nargin == 2
o.var = varargin{1};
o.b= varargin{2};
else
error("the nuber of arguments do not match!")
end
end
end
end
>>x=inputClass([1 2 3],2)
x =
inputClass with properties:
var: [1 2 3]
b: 2

  2 Comments

Guillaume
Guillaume on 10 Jul 2019
"The defination of var is wrong."
From a pure matlab point of view (ignoring coder), there is nothing wrong with the definition of var. Can you explain what you mean by that?
Sayyed Ahmad
Sayyed Ahmad on 10 Jul 2019
you can def. a variable without dimension or a fix dimension. But a def. like var(:,1) could not be handel by compeiler.
Compeiler could be handel a calling of variable by var(:,1) but not the def. of variable.

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