How can I resolve this problem regarding nested functions?

function [root1, root2]= getreal(a,b,c);
getinput
   function getinput 
       if a==0 
           disp('Error')
       end
   end
  
root1 = ((0-b) + sqrt(D))/2*a
root2 = ((0-b) - sqrt(D))/2*a 
   function calcdisc = D
       disc = (b*b)-(4*a*c);
       calcdisc = disc;
   end  

end

When I enter >>getreal(0,1,1), the script still manages to calculate for root1 and root 2.

function [root1, root2]= getreal(a,b,c);
getinput
   function getinput 
       if a==0 
           disp('Error')
       else
           root1 = ((0-b) + sqrt(D))/2*a
           root2 = ((0-b) - sqrt(D))/2*a 
           function calcdisc = D
           disc = (b*b)-(4*a*c);
           calcdisc = disc;
           end
       end
   end
end

However, when I tried this solution, it displayed this error message

'Error: File: getreal.m Line: 10 Column: 12

Function definition is misplaced or improperly nested.'

Answer 1

[Geoff Hayes]

Cyrus - from Requirements for Nested Functions, You cannot define a nested function inside any of the MATLAB® program control statements, such as if/elseif/else, switch/case, for, while, or try/catch. You have nested the function within the else block.

Answer 2

[David Hill]

I assume you can use a nested anonymous function. Sounds like your getinput function needs to get all of the coefficients and check to make sure a~=0.

function [root1, root2]= getreal()
calcdisc=@(a)a(2)^2-4*a(1)*a(3);
    function a=getinput()
        a(1)=0;
        while ~a(1)
            a=input('Input quadratic coefficients in the form of an array, [a,b,c] (a~=0): ');
        end
    end
a=getinput();
root1=(-a(2)+sqrt(calcdisc(a))/(2*a(1)));
root2=(-a(2)-sqrt(calcdisc(a))/(2*a(1)));
end

Answer 3

[Steven Lord]

Your first attempt is pretty close. Just a couple comments:

function [root1, root2]= getreal(a,b,c);
getinput
   function getinput 
       if a==0 
           disp('Error')

disp doesn't stop execution of the function. You probably want your getinput function to stop execution if a is equal to 0. For that you should call the error function.

       end
   end
  
root1 = ((0-b) + sqrt(D))/2*a
root2 = ((0-b) - sqrt(D))/2*a 
   function calcdisc = D

This defines a function named D that returns a variable calcdisc. You probably want to reverse those, to define a function named calcdisc that returns a variable D.

function D = calcdisc

This will require changes to the body of the calcdisc function and to how you call it.

       disc = (b*b)-(4*a*c);
       calcdisc = disc;
   end  

end