Question

The main problem here is to evaluate the user function at some point because we don’t know if the user will enter a function in x domain or another domain

I tried this but it doesn’t work:

function y = f(~)
y = input('Enter you function: ');
end

and this is what I want:

>>f
Enter you function: a^2+3*a-3
>>f(1)
ans =
1

Answer 1

This solution almost provides the exact requirements in your question. I’d feel kind of queezy using this though with the EVAL. You’d also want to wrap some error checking into this.

classdef f < handle

    properties (Access = private)
        functionString = '';
    end

    methods
        function obj = f
            if nargin == 0
                obj.functionString = input('Enter your function: ', 's');
            end
        end

        function value = subsref(obj, a)
            a = a.subs{:};
            value = eval(obj.functionString);
        end

        function display(obj)

        end
    end

end

You can then use this class like:

>> a = f
Enter your function: a^2+3*a-3
>> a(1)

ans =

     1

>> a(2)

ans =

     7