get number of output arguments of a function handle

Is there a better way to get the number of output arguments (should be one or two) of a function handle than this:

a = 1;

b = 2;

x0 = 0;

fun = @(x) function_file(x,a,b);

try

[f1,f2] = fun(x0);

nout = 2;

catch

nout = 1;

end

It should also work if the function is:

fun = @(x) a*x.^b;

Therefore catching the name 'function_file' using functions(fun) and then use nargout('function_file') is not an option.

Thanks in advance!

Alwin

Answer 1

[Steven Lord]

Calling nargout on the function handle itself may give an answer.

nargout(@sin) % The sin function returns 1 output

ans = 1

But it may not be possible to tell from the function handle with how many outputs it can be called.

nargout(@size) % Can be called with an arbitrary number of output arguments

ans = -1

I believe calling nargout on an anonymous functions always returns -1 because MATLAB can't tell with how many output arguments the code that makes up the body of the anonymous function can be called until you actually call it.

f = @(x) svd(x);
nargout(f)

ans = -1

A = magic(4);

% Call f with 1 output
s = f(A)

s = 4×1

34.0000 17.8885 4.4721 0.0000

% Call f with three outputs
[u, s, v] = f(A)

u = 4×4

-0.5000 0.6708 0.5000 -0.2236 -0.5000 -0.2236 -0.5000 -0.6708 -0.5000 0.2236 -0.5000 0.6708 -0.5000 -0.6708 0.5000 0.2236

s = 4×4

34.0000 0 0 0 0 17.8885 0 0 0 0 4.4721 0 0 0 0 0.0000

v = 4×4

-0.5000 0.5000 0.6708 -0.2236 -0.5000 -0.5000 -0.2236 -0.6708 -0.5000 -0.5000 0.2236 0.6708 -0.5000 0.5000 -0.6708 0.2236