Re: more help needed with function handles

[John W. Eaton]

On 3/25/20 2:42 PM, "Markus Mützel" wrote:

> > It is surprisingly hard to find a built-in function that accepts a double input 
> > that is not implemented as a class method.
> > I finally tried with "isstr" (diary5). I hope that helps.

We could also try with an argument that is something other than double.

> And another one without the "clear functions" (diary6).

I don't see any difference between those last two cases other than the 
"clear functions" command (which is fine).

I think I see what's happening now.  Thanks.

It's interesting that functions (@sin) shows an empty "file" field but 
functions (@isstr) says "MATLAB built-in function".  Also, sin is shown 
as being a builtin in @double, but isstr is not in an '@' directory (not 
that they are actually there, I suppose it is just a convention for 
marking built-in functions with the classes they accept).

Octave already has a way to mark built-in functions with the classes 
they accept but only a few functions are tagged so far.  For example, in 
libinterp/corefcn/svd.cc:


  DEFUN (svd, args, nargout,
         classes: double single
         doc: /* -*- texinfo -*-
         ...

the "classes:" line is used to insert the "double" and "single" class 
names in a table that is later used when searching for functions.  The 
"sin" function in Octave is not marked this way.  So if you execute the 
original test in Octave, it will do something different from Matlab, but 
if you change the test to use svd instead of sin, it will be closer to 
(I think maybe the same as) what Matlab does.

jwe