# HG changeset patch
# User Ben Abbott  <bpabbott@mac.com>
# Date 1314048284 14400
# Node ID 5e37369ea13c0a404ca7e791e393029a16e8279d
# Parent  4ec4096f65d1e40eddcaedd9d6a8e292cfecc47e
polyval.m: Return zeros when polynomial is empty (ML Compatibility).
           Clarify and improve syntax check.
           Add Demos.

diff --git a/scripts/polynomial/polyval.m b/scripts/polynomial/polyval.m
--- a/scripts/polynomial/polyval.m
+++ b/scripts/polynomial/polyval.m
@@ -20,7 +20,7 @@
 ## @deftypefn  {Function File} {@var{y} =} polyval (@var{p}, @var{x})
 ## @deftypefnx {Function File} {@var{y} =} polyval (@var{p}, @var{x}, [], @var{mu})
 ## Evaluate the polynomial @var{p} at the specified values of @var{x}.  When
-## @var{mu} is present evaluate the polynomial for
+## @var{mu} is present, evaluate the polynomial for
 ## (@var{x}-@var{mu}(1))/@var{mu}(2).
 ## If @var{x} is a vector or matrix, the polynomial is evaluated for each of
 ## the elements of @var{x}.
@@ -39,17 +39,19 @@
 ## Created: June 1994
 ## Adapted-By: jwe
 
-function [y, dy] = polyval (p, x, s, mu)
+function [y, dy] = polyval (p, x, s = [], mu)
 
   if (nargin < 2 || nargin > 4 || (nargout == 2 && nargin < 3))
     print_usage ();
   endif
 
-  if (nargin < 3)
-    s = [];
-  endif
-
-  if (! (isvector (p) || isempty (p)))
+  if (isempty (x))
+    y = [];
+    return;
+  elseif (isempty (p))
+    y = zeros (size (x));
+    return;
+  elseif (! isvector (p))
     error ("polyval: first argument must be a vector");
   endif
 
@@ -57,16 +59,6 @@
     x = (x - mu(1)) / mu(2);
   endif
 
-  if (isempty (x))
-    y = [];
-    return;
-  endif
-
-  if (length (p) == 0)
-    y = p;
-    return;
-  endif
-
   n = length (p) - 1;
   y = p(1) * ones (size (x));
   for i = 2:n+1
@@ -80,10 +72,23 @@
     ##   dy = t * sqrt (1 + sumsq (A/s.R, 2)) * s.normr / sqrt (s.df)
     ## If my inference is correct, then t must equal 1 for polyval.
     ## This is because finv (0.5, n, n) = 1.0 for any n.
-    k = numel (x);
-    A = (x(:) * ones (1, n+1)) .^ (ones (k, 1) * (n:-1:0));
-    dy = sqrt (1 + sumsq (A/s.R, 2)) * s.normr / sqrt (s.df);
-    dy = reshape (dy, size (x));
+    try
+      k = numel (x);
+      A = (x(:) * ones (1, n+1)) .^ (ones (k, 1) * (n:-1:0));
+      dy = sqrt (1 + sumsq (A/s.R, 2)) * s.normr / sqrt (s.df);
+      dy = reshape (dy, size (x));
+    catch
+      if (isempty (s))
+        error ("polyval: third input is required.")
+      elseif (isstruct (s)
+              && all (ismember ({"R", "normr", "df"}, fieldnames (s))))
+        error (lasterr ())
+      elseif (isstruct (s))
+        error ("polyval: third input is missing the required fields.");
+      else
+        error ("polyval: third input is not a structure.");
+      endif
+    end_try_catch
   endif
 
 endfunction
@@ -142,3 +147,6 @@
 %! assert (y, polyval(p,x), eps)
 %! x = reshape(x, [1, 1, 5, 2]);
 
+%!assert (zeros (1, 10), polyval ([], 1:10))
+%!assert ([], polyval (1, []))
+%!assert ([], polyval ([], []))