How to use nested functions to build a code that compares inputs

I am somewhat of a newbie. I am writing a code that acts as an autograder with the following requirements. The function tests two functions (the student's solution and the instructor's reference solution) by calling them repeatedly with various input arguments and comparing the results. Both functions are assumed to take exactly one input argument. The inputs are two function handles followed by a variable number of additional input arguments. This grader function must call the two functions with each of the supplied input arguments one by one. If the results match all test cases, i.e. for each input argument, the grader function returns logical 'true'. Otherwise, it returns 'false'. Comparison must work for both arrays and scalars.

I have been working on the following code, which works for inputs like:

grader(@sin,@max,0)

grader(@sin,@max,0,1)

but not for inputs like:

grader(@cos,@cos,0,1,[-pi,0,pi])

Please help! Thank you.

function result = grader(a,b, varargin)

result = true;
in = varargin;
for ii = in{1}:in{end}
	A = a(ii);
	B = b(ii);
end

if isequal(A,B)
	result = true;
else	result = false;

end
end

[Stephen23]

Although the title is "How to use nested functions to build a code that compares inputs", nothing in your question seems to be related to nested functions: https://www.mathworks.com/help/matlab/matlab_prog/nested-functions.html

Note that the colon operation here:

in{1}:in{end}

is very unlikely to be useful for you: in some cases you will get an error, in other cases you will get a vector of values which may or may not be provided as input values. In MATLAB it is usually best to iterate over indices, not data values.

[Gin]

Wow, thank you for your help. Now that you mentioned it, would a plausible solution consist of a nested function? Say, the function that compares the results -- can it be nested within the main grader function?

[Gin]

Ah okay, nevermind. Thanks again!

Answer 1

[Stephen23]

The comparison needs to be inside the loop (not after the loop):

function result = grader(funA, funB, varargin)
result = true;
for k = 1:numel(varargin)
    A = funA(varargin{k});
    B = funB(varargin{k});
    if ~isequal(A,B)
        result = false;
        return % no point in continuing, might as well exit now.
    end
end

Giving:

>> grader(@sin,@max,0)
ans =
     1
>> grader(@sin,@max,0,1)
ans =
     0
>> grader(@cos,@cos,0,1,[-pi,0,pi])
ans =
     1

[Sri sai teja Palisetti]

Thankyou , so much stefen it helped me to submit my assignment.

[Abdul Hanan Wali]

function grader(a,b, c)

testcode(a, c);

testcode2(b, c);

if isequal ( testcode== testcode2)

true

else

false

end

function valOut = testcode(funcIn , numIn)

valOut = funcIn(numIn);

end

function output = testcode2( func, value)

output = func(value);

end

end

[Abdul Hanan Wali]

somehow this code will run? I am not able to compare the functions

[Aravind Gopal]

Can someone tell me why this code is giving me an error

 function result = grader(st_fun , ins_fun, varargin)
  result = true;
  for ii = 1:nargin
     var_1 = st_fun(varargin{ii});
     var_2 = ins_fun(varargin{ii});
     if ~isequal(var_1,var_2)
     result =false;
       return 
     end

  end
  end

It showed index exceeds the number of array elements. Index must not exceed 1.

error in grader(line 4)

var_1 = st_fun(varargin{ii})

[Stephen23]

"Can someone tell me why this code is giving me an error"

for ii = 1:nargin
%          ^^^^^^ because of this.

Count how many inputs your function has. Count how many elements VARARGIN has.

[Otto Alfonso]

'nargin' not only counts the input values of 'varargin', but also the other inputs (st_fun, ins_fun)

You need to either substract the amount of other inputs:

for ii = 1:(nargin-2)
% In this case 2 because of the other 2 inputs

Or to use a function that counts the elements ('length', 'size', 'numel')

Answer 2

[Rasheed Aiyedun]

function out = grader(a,b,varargin)
out = true

for ii = 1:length(varargin)
    c = varargin{ii};
    d = a(c);
    e = b(c);
    if d == e
        out = true;
    else
        out = false
    end
end
end