--- a/scripts/quaternion/quaternion.m
+++ b/scripts/quaternion/quaternion.m
@@ -1,86 +1,116 @@
-function [a,b,c,d] = quaternion(w,x,y,z)
-# quaternion: construct or extract a quaternion
-#  w = a*i + b*j + c*k + d from given data.
-#
-# calling formats:
-# [a,b,c,d]   = quaternion(w)           -or-
-# [vv,theta] = quaternion(w)
-# w           = quaternion(a,b,c,d)
-# w           = quaternion(vv,theta)
+## Copyright (C) 1998 Auburn University.  All rights reserved.
+##
+## This file is part of Octave.
+##
+## Octave is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 2, or (at your option)
+## any later version.
+##
+## Octave is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+## General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with Octave; see the file COPYING.  If not, write to the Free
+## Software Foundation, 59 Temple Place - Suite 330, Boston, MA
+## 02111-1307, USA.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {[@var{a}, @var{b}, @var{c}, @var{d}] =} quaternion (w)
+## @deftypefnx {Function File} {[@var{vv}, @var{theta}] =} quaternion (w)
+## @deftypefnx {Function File} {@var{w} =} quaternion (@var{a}, @var{b}, @var{c}, @var{d})
+## @deftypefnx {Function File} {@var{w} =} quaternion (@var{vv}, @var{theta})
+## Construct or extract a quaternion
+##
+## @example
+## w = a*i + b*j + c*k + d
+## @end example
+##
+## @noindent
+## from given data.
+## @end deftypefn
+
+## Author: A. S. Hodel <a.s.hodel@eng.auburn.edu>
+## Adapted-By: jwe
+
+function [a, b, c, d] = quaternion (w, x, y, z)
+
+  switch (nargin)
+    case(1)
+      if (! (is_vector (w) && length (w) == 4))
+	error ("input vector must be of length 4)");
+      endif
+      ## extract data
+      switch (nargout)
+	case(4)
+	  a = w(1);
+	  b = w(2);
+	  c = w(3);
+	  d = w(4);
 
-switch(nargin)
-case(1),                                        # extract information
-  if(!(is_vector(w) & length(w) == 4) )
-    error("input vector must be of length 4)")
-  endif
-  # extract data
-  switch(nargout)
-  case(4),
-    a = w(1);
-    b = w(2);
-    c = w(3);
-    d = w(4);
-  case(2),
-    if(abs(norm(w)-1) > 1e-12)
-      warning(sprintf("quaternion: ||w||=%e, setting=1 for vv, theta",norm(w)))
-      w = w/norm(w);
+	case(2)
+	  if (abs (norm (w) - 1) > 1e-12)
+	    warning ("quaternion: ||w||=%e, setting=1 for vv, theta", norm(w));
+	    w = w/norm(w);
+	  endif
+	  [a, b, c, d] = quaternion (w);
+	  theta = acos (d) * 2;
+	  if (abs (theta) > pi)
+	    theta = theta - sign (theta) * pi;
+	  endif
+	  sin_th_2 = norm ([a, b, c]);
+
+	  if (sin_th_2 != 0)
+	    vv = [a, b, c] / sin_th_2;
+	  else
+	    vv = [a, b, c];
+	  endif
+	  a = vv;
+	  b = theta;
+	otherwise
+	  usage ("[a, b, c, d] = quaternion (w) or [vv, theta] = quaternion (w)");
+      endswitch
+
+  case(2)
+    if (nargout != 1)
+      usage ("w = quaterion (vv, theta)");
     endif
-    [a,b,c,d] = quaternion(w);
-    theta = acos(d)*2;
-    if(abs(theta) > pi)
-      theta = theta - sign(theta)*pi;
+    vv = w;
+    theta = x;
+
+    if (! is_vector (vv) || length (vv) != 3)
+      error ("vv must be a length three vector");
+    elseif (! is_scalar (theta))
+      error ("theta must be a scalar");
+    elseif (norm (vv) == 0)
+      error ("quaternion: vv is zero.");
+    elseif (abs (norm (vv) - 1) > 1e-12)
+      warning ("quaternion: ||vv|| != 1, normalizing")
+      vv = vv / norm (vv);
     endif
-    sin_th_2 = norm([a, b, c]);
 
-    if(sin_th_2 != 0)
-      vv = [a,b,c]/sin_th_2;
-    else
-      vv = [a, b, c];
+    if (abs (theta) > 2*pi)
+      warning ("quaternion: |theta| > 2 pi, normalizing")
+      theta = rem (theta, 2*pi);
     endif
-    a = vv;
-    b = theta;
-  otherwise,
-    usage("[a,b,c,d] = quaternion(w) or [vv,theta] = quaternion(w)");
+    vv = vv * sin (theta / 2);
+    d = cos (theta / 2);
+    a = quaternion (vv(1), vv(2), vv(3), d);
+
+  case(4)
+    if (nargout != 1)
+      usage ("w = quaterion (a, b, c, d)");
+    endif
+    if (! (is_scalar (w) && is_scalar (x) && is_scalar (y) && is_scalar (z)))
+      error ("input values must be scalars.");
+    endif
+    a = [w, x, y, z];
+
+  otherwise
+    error ("usage: [a, b, c, d] = quaternion (w), a = quaternion (w, x, y, z)");
+
   endswitch
 
-case(2),
-  if(nargout != 1)
-    usage("w = quaterion(vv,theta)");
-  endif
-  vv = w;
-  theta = x;
-
-  if(!is_vector(vv) | length(vv) != 3)
-    error("vv must be a length three vector")
-  elseif(!is_scalar(theta))
-    error("theta must be a scalar");
-  elseif(norm(vv) == 0)
-    error("quaternion: vv is zero.")
-  elseif(abs(norm(vv)-1) > 1e-12)
-    warning("quaternion: ||vv|| != 1, normalizing")
-    vv = vv/norm(vv);
-  endif
-
-  if(abs(theta) > 2*pi)
-    warning("quaternion: |theta| > 2 pi, normalizing")
-    theta = rem(theta,2*pi);
-  endif
-  vv = vv*sin(theta/2);
-  d = cos(theta/2);
-  a = quaternion(vv(1), vv(2), vv(3), d);
-
-case(4),
-  if(nargout != 1)
-    usage("w = quaterion(a,b,c,d)");
-  endif
-  if ( !(is_scalar(w) & is_scalar(x) & is_scalar(y) & is_scalar(z)) )
-    error("input values must be scalars.")
-  endif
-  a = [w, x, y, z];
-
-otherwise,
-  error("usage: [a,b,c,d] = quaternion(w), a = quaternion(w,x,y,z)")
-
-endswitch
-
 endfunction