Not enough arguments error when I clearly supply enough arguments?

I have two functions

function coords = dart_gun01(n)
  coords = normrnd(0,10,n,2);
end

and

function [total, tally, shots] = dart_score(n, f_dart)
  shots = f_dart(n);
  total = 0;
  tally = zeros(1,4);
  for i=1:n
    r = (shots(i,1)^2 + shots(i,2)^2)^0.5;
    if r < 1
      total = total + 10;
      tally(4) = tally(4) + 1;
    else if r < 5
      total = total + 5;
      tally(3) = tally(3) + 1;
    else if r < 10
      total = total + 1;
      tally(2) = tally(2) + 1;
    else
      tally(1) = tally(1) + 1;
    end
  end
end

They are meant to work together; the first function is inputted into the second as the argument f_dart. But when I try to call for example:

[total,tally,shots] = dart_score(10,dart_gun01);

I get a not enough arguments error with regards to the dart_gun01 function. I don't why this is happening. for a while is was not working, then it started working, and now it's not working and the whole time I have not changed anything. Why is this?

Answer 1

[Stephen23]

Try supplying the supplementary function dart_gun01 as a function handle:

[total,tally,shots] = dart_score(10,@dart_gun01);

Currently what you are doing is this:

[total,tally,shots] = dart_score(10,dart_gun01);

MATLAB looks through the list of input arguments. The first is a numeric value, so no problem there. The second it identifies as a function call, and so it immediately evaluates that function right there, before it even gets started with dart_score. It is exactly as if you call this:

dart_gun01

and you will get the same error: the function is being evaluated and you are not giving it the required arguments. Using a function handle tells MATLAB that you want to pass the function as a variable, and not evaluate it where it appears. More info and examples:

http://www.mathworks.com/help/matlab/matlab_prog/applications-of-function-handles.html

http://www.mathworks.com/help/matlab/matlab_prog/calling-a-function-using-its-handle.html