Unexpected behavior with built-in

[John W. Eaton]

On 22-Jul-2009, Jaroslav Hajek wrote:

| It's not just feval, but also str2func. Currently, feval(str,...)
| works like feval(str2func(str),...), which is OK, but leads to
| problems.
| 
| This works OK with 3.2.x:
| 
| function y = my_eval (x)
|   y = sin(x) - 0.5;
| endfunction
| 
| fzero ("my_eval", 0)
| 
| but watch this seemingly innocent change:
| 
| function y = guarded_eval (x)
|   y = sin(x) - 0.5;
| endfunction
| 
| fzero ("guarded_eval", 0)
| 
| Surprise! This fails in an incomprehensible way. Your guess is right:
| guarded_eval is a subfunction in fzero.
| I don't stand by that making feval ignore subfunctions and private
| functions is the best solution. Thinking about this, it will actually
| bring a lot of trouble for Pytave and other embedded applications of
| Octave, which use feval to access functions that may be defined
| locally.
| But surely Octave should provide a way out of this, even if Matlab
| doesn't (does Matlab's str2func ignore subfunctions?).

I think the solution is to use function handles and avoid using simple
names to refer to functions.  OO methods can cause trouble currently,
but I think using function handles should work properly for other
cases now.

jwe