How to make user-defined type pass as numeric?

Suppose I have a defined type that behaves like a number. I would like it to pass the test:

validateattributes(x, {'numeric'}, {})

It's not enough, apparently, to overload the function isnumeric.m. What else needs to be done?

Thanks, n

Answer 1

[Geoff Hayes]

Naor - try overloading the isa function instead. For example, let's suppose that the following class is "numeric".

classdef MyNumberClass
   properties
      x
   end
   methods

        function obj = MyNumberClass(varargin)
           if nargin > 0
              obj.x = 42;
           else
              obj.x = 99;
           end
        end

        function [result] = isa(obj,typeStr)
           result = false;
           if strcmpi(typeStr,'numeric') || strcmpi(typestr,'MyNumberClass')
              result = true;
           end
        end

     end
  end

Then in the Command Window, try the following

 myInstance = MyNumberClass;

Now try to validate it as

 validateattributes(myInstance, {'numeric'}, {})

No error is thrown and so the object is considered to be numeric. Note that you would need to overload isnumeric so that that function "passes" too.

[Naor Movshovitz]

Thanks Geoff,

This does what I wanted so I accepted the answer. If you can, please edit your answer to make the overloaded isa() method return true also on type MyNumberClass.

One tiny corner that is not really that important but would be nice to know how to fix is the error message generated when validateattributes fails:

validateattributes('s',{'numeric'},{})

Expected input to be one of these types:

double, single, uint8, uint16, uint32, uint64, int8, int16, int32, int64

Instead its type was char.

It would be nice if the message mentioned MyNumberClass at the end.

[Geoff Hayes]

Naor - I've updated the solution with your suggestion. As for including your class in the error output, I'm not sure how that can be done.