Re: is a piece of code in 'polyval' really needed ?

[Ben Abbott]

On Aug 18, 2011, at 1:34 PM, Bård Skaflestad wrote:

> On Thu, 2011-08-18 at 18:49 +0200, Ben Abbott wrote:
>> On Aug 18, 2011, at 11:31 AM, Sergei Steshenko wrote:
>> 
>>> Hello,
>>> 
>>> looking at 'polyval' implementation in octave-3.4.2 I see this:
>>> 
>>> <snip>
>>> 
>>> Is this:
>>> 
>>>     65   if (length (p) == 0)
>>>     66     y = p;
>>>     67     return;
>>>     68   endif
>>> 
>>> really needed ? My point is that, if I understand correctly,
>>> 
>>>     52   if (! (isvector (p) || isempty (p)))
>>> 
>>> check won't let code on lines ##65 .. 68 to be executed.
> 
> [ snip ]
> 
>> You are correct. Lines 65-68 aren't needed.
> 
> Actually, they are.  Reread the actual check.

Thanks for catching that. Perhaps the syntax checking should be made more clear?

 42 function [y, dy] = polyval (p, x, s = [], mu)
 43 
 44   if (nargin < 2 || nargin > 4 || (nargout == 2 && nargin < 3))
 45     print_usage ();
 46   endif
 47 
 48   if (isempty (x))
 49     y = [];
 50     return;
 51   elseif (isempty (p))
 52     y = p;
 53     return;
 54   elseif (! isvector (p))
 55     error ("polyval: first argument must be a vector");
 56   endif
 57 
 58   if (nargin > 3)
 59     x = (x - mu(1)) / mu(2);
 60   endif

Ben