--- a/scripts/control/system/zpout.m	Fri Jul 11 17:46:41 2003 +0000
+++ b/scripts/control/system/zpout.m	Fri Jul 11 18:37:48 2003 +0000
@@ -29,79 +29,82 @@
 
 function zpout (zer, pol, k, x)
 
-  save_empty = empty_list_elements_ok;
-  empty_list_elements_ok = 1;
+  save_warn_empty_list_elements = warn_empty_list_elements;
+  unwind_protect
+    warn_empty_list_elements = 0;
 
-  if (nargin < 3 ) | (nargin > 4) | (nargout != 0 )
-    usage("zpout(zer,pol,k[,x])");
-  endif
+    if (nargin < 3 ) | (nargin > 4) | (nargout != 0 )
+      usage("zpout(zer,pol,k[,x])");
+    endif
 
-  if( !(isvector(zer) | isempty(zer)) | !(isvector(pol) | isempty(pol)) )
-    error("zer, pol must be vectors or empty");
-  endif
+    if( !(isvector(zer) | isempty(zer)) | !(isvector(pol) | isempty(pol)) )
+      error("zer, pol must be vectors or empty");
+    endif
 
-  if(!isscalar(k))
-    error("zpout: argument k must be a scalar.")
-  endif
+    if(!isscalar(k))
+      error("zpout: argument k must be a scalar.")
+    endif
 
-  if (nargin == 3)
-    x = "s";
-  elseif( ! isstr(x) )
-    error("zpout: third argument must be a string");
-  endif
+    if (nargin == 3)
+      x = "s";
+    elseif( ! isstr(x) )
+      error("zpout: third argument must be a string");
+    endif
 
-  numstring = num2str(k);
+    numstring = num2str(k);
 
-  if(length(zer))
-    ## find roots at z,s = 0
-    nzr = sum(zer == 0);
-    if(nzr)
-      if(nzr > 1)
-        numstring = [numstring,sprintf(" %s^%d",x,nzr)];
-      else
-        numstring = [numstring,sprintf(" %s",x)];
+    if(length(zer))
+      ## find roots at z,s = 0
+      nzr = sum(zer == 0);
+      if(nzr)
+	if(nzr > 1)
+	  numstring = [numstring,sprintf(" %s^%d",x,nzr)];
+	else
+	  numstring = [numstring,sprintf(" %s",x)];
+	endif
       endif
+      zer = sortcom(-zer);
+      for ii=1:length(zer)
+	if(zer(ii) != 0)
+	  numstring = [numstring,sprintf(" (%s %s)",x,com2str(zer(ii),1) ) ];
+	endif
+      endfor
     endif
-    zer = sortcom(-zer);
-    for ii=1:length(zer)
-      if(zer(ii) != 0)
-        numstring = [numstring,sprintf(" (%s %s)",x,com2str(zer(ii),1) ) ];
-      endif
-    endfor
-  endif
 
-  if(length(pol))
-    ## find roots at z,s = 0
-    nzr = sum(pol == 0);
-    if(nzr)
-      if(nzr > 1)
-        denomstring = [sprintf("%s^%d",x,nzr)];
+    if(length(pol))
+      ## find roots at z,s = 0
+      nzr = sum(pol == 0);
+      if(nzr)
+	if(nzr > 1)
+	  denomstring = [sprintf("%s^%d",x,nzr)];
+	else
+	  denomstring = [sprintf("%s",x)];
+	endif
       else
-        denomstring = [sprintf("%s",x)];
+	denomstring = " ";
+      endif
+      pol = sortcom(-pol);
+      for ii=1:length(pol)
+	if(pol(ii) != 0)
+	  denomstring = [denomstring,sprintf(" (%s %s)",x,com2str(pol(ii),1))];
+	endif
+      endfor
+    endif
+
+    len = max(length(numstring),length(denomstring));
+    if(len > 0)
+      y = strrep(blanks(len)," ","-");
+      disp(numstring)
+      if(length(denomstring))
+	disp(y)
+	disp(denomstring)
       endif
     else
-      denomstring = " ";
-    endif
-    pol = sortcom(-pol);
-    for ii=1:length(pol)
-      if(pol(ii) != 0)
-        denomstring = [denomstring,sprintf(" (%s %s)",x,com2str(pol(ii),1))];
-      endif
-    endfor
-  endif
+      error ("zpout: empty transfer function")
+    end
 
-  len = max(length(numstring),length(denomstring));
-  if(len > 0)
-    y = strrep(blanks(len)," ","-");
-    disp(numstring)
-    if(length(denomstring))
-      disp(y)
-      disp(denomstring)
-    endif
-  else
-    error ("zpout: empty transfer function")
-  end
-
-  empty_list_elements_ok = save_empty;
+  unwind_protect_cleanup
+    warn_empty_list_elements = save_warn_empty_list_elements;
+  end_unwind_protect
 
 endfunction