nargin vs exist

Question

Given a function like:

function foo(myParam)
if nargin<1
  myParam = \'default value\';
end % if
end % function

I\'ve seen people use so

Answer 1

Both should work. But...

Exist tends to be slow, since it must look through your workspace for the variable in question. When you write error checks like this, you don't want them to suck up CPU cycles. The test against nargin is a simple test against a single numeric value.

I'd also generally suggest a more extensive test. Something like

if (nargin<1) || isempty(myparam)

  myparam = defaultvalue;

elseif

  ...

end

Inside the elseif branch, I'll put a set of additional tests to see if the parameter has the expected size, shape, class of variable, etc. If those tests fail, I'll return a friendly error message that explains what was wrong.