MATLAB: How to overload built-in MATLAB functions

builtfunctioninMATLABoverloadoverloadedoverloading

I would like to overload built-in MATLAB functions with my own functions. For example, when I execute the command:

x = rand(100);

I would like MATLAB to call my RAND function rather than the built-in MATLAB RAND function.

Best Answer

To overload the RAND function with your own function myrand.m, place myrand.m in a directory on the MATLAB path. Then, create the following function and save it as rand.m:

function varargout = rand(varargin)
[varargout{1:nargout}] = myrand(varargin{:});

The built-in RAND function accepts both double and char inputs. Therefore, you will need this to save this file in a directory named @double and a directory named @char.

If the state of the new RAND is other than double datatype (e.g., uint32) you will have to create another copy of rand.m in another @<class> directory. Note that it is not recommended to have more than one @double directory on your search path, as this can create confusion on which @double folder is being used. Place all files overloaded for a specific data type <foo> within the same @<foo> directory.

The on-line documentation containing information about function overloading can be found at:

https://www.mathworks.com/help/matlab/matlab_oop/overloading-functions-for-your-class.html

If you would like to use the Launch Pad in MATLAB 6.x and higher to find this information, follow this menu path:

MATLAB Help --> Using MATLAB --> Programming and Data Types --> MATLAB Classes and Objects --> Overloading Operators and Functions.

Alternatively, you could also search for "overloading" in the documentation by using the search tab in the Help Browser.

Related Solutions

MATLAB: Are .m files in a subfolder of a class folder considered methods of that class

Files in a subfolder of a class folder are not considered methods of the class.

Please refer to the following example:

@myClass > myClass.m:

classdef myClass
    methods
        function classObj = myClass()
            classObj.method1()
            classObj.method2()
        end
    end
end

@myClass > method1.m:

function method1(classObj)
    disp('method in class folder')
end

@myClass > subfolder > method2.m:

function method2(classObj)
    disp('method in subfolder')
end

-----

>> m = myClass
method in class folder

Unrecognized method, property or field 'method2' for class 'myClass'.

Error in myClass (line 5)

classobj.method2()

As you can see, 'method1' is part of the class, but 'method2', which is in a subfolder of '@myClass', is not treated as a method of the class.

For more details about using class folders in MATLAB, please see the following documentation page:

https://www.mathworks.com/help/matlab/matlab_oop/organizing-classes-in-folders.html

MATLAB: How to return NaN when NaN is compared to any other variable in MATLAB 7.5 (R2007b)

It is possible to override the logical operators like '>' (greater than) and '<' (less than) in MATLAB. When applying a logical operator MATLAB looks for an M-function with a specific name corresponding to the operation defined for an object of the class being compared (in this case, the class would be double). To overload the built-in function, create a custom function, named gt.m (to overload >) in a @double directory on the MATLAB path. This file will then be called with two inputs when MATLAB executes a statement like

 a > b

Steps:

1. First, for accepting double input variables, create a folder named: "@double" (without quotes)

2. Inside this directory, create a file named "gt.m" and input the following code:

function C = gt(A,B)

if any(isnan([A B]))

    C =NaN;

else

    C = builtin('gt',A,B);

end

3. Now edit the MATLAB path to bring the folder in which @double folder exists, at the top most level

4. Verify if your gt.m is ahead of the others by executing :

which-all gt.m

at the MATLAB command prompt and check if the folder containg @double appears before the built-in gt.m files

5. Now restart MATLAB and execute the following to check if the code works fine:

3>NaN

6. Similarly, if you wish, you can override the following files as well:

lt ('<'), le ('<='), ne ('!='), eq ('==')

Best Answer

Related Solutions

MATLAB: Are .m files in a subfolder of a class folder considered methods of that class

MATLAB: How to return NaN when NaN is compared to any other variable in MATLAB 7.5 (R2007b)

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