# HG changeset patch
# User Jaroslav Hajek <highegg@gmail.com>
# Date 1243926409 -7200
# Node ID 226f6d001ee2d28abd7518f65257145edfc4d35b
# Parent  567e3e4ab74debb5753c14eb50c7925ca8fd9fac
further improve the polynomial example, fix indexing

diff --git a/ChangeLog b/ChangeLog
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2009-06-02  Jaroslav Hajek  <highegg@gmail.com>
+
+	* examples/@polynomial/subsref.m: Allow chained subscripts,
+	fix behavior according to docs.
+	* examples/@polynomial/subsasgn.m: Allow chained subscripts,
+	fix behavior according to docs.
+
 2009-06-02  Robert T. Short  <octave@phaselockedsystems.com>
 
 	* examples/@polynomial: Remove tabs from all functions so
diff --git a/doc/ChangeLog b/doc/ChangeLog
--- a/doc/ChangeLog
+++ b/doc/ChangeLog
@@ -1,3 +1,8 @@
+2009-06-02  Jaroslav Hajek  <highegg@gmail.com>
+
+	* interpreter/oop.txi: Update docs of polynomial class, mention
+	chained indexing.
+
 2009-05-25  Rik  <rdrider0-list@yahoo.com>
 
 	* interpreter/Makefile.in: Add texmf.cnf to list of distributed files
diff --git a/doc/interpreter/oop.txi b/doc/interpreter/oop.txi
--- a/doc/interpreter/oop.txi
+++ b/doc/interpreter/oop.txi
@@ -264,7 +264,7 @@
 @DOCSTRING(subsref)
 
 For example we might decide that indexing with "()" evaluates the
-polynomial and indexing with "@{@}" returns the @var{n}-th coefficient.
+polynomial and indexing with "@{@}" returns the @var{n}-th coefficient (of @var{n}-th power).
 In this case the @code{subsref} method of our polynomial class might look like
 
 @polynomialfile{subsref.m}
@@ -274,6 +274,11 @@
 
 @DOCSTRING(subsasgn)
 
+Note that the @code{subsref} and @code{subsasgn} methods always receive the
+whole index chain, while they usually handle only the first element.  It is the
+responsibility of these methods to handle the rest of the chain (if needed),
+usually by forwarding it again to @code{subsref} or @code{subsasgn}.
+
 If you wish to use the @code{end} keyword in subscripted expressions
 of an object, then the user needs to define the @code{end} method for 
 the class.
diff --git a/examples/@polynomial/end.m b/examples/@polynomial/end.m
--- a/examples/@polynomial/end.m
+++ b/examples/@polynomial/end.m
@@ -1,13 +1,9 @@
 function r = end (obj, index_pos, num_indices)
 
-  if ( num_indices!=1 )
+  if (num_indices != 1)
     error ("polynomial object may only have one index")
   endif
   
-  if ( (index_pos<1) || (index_pos>length(obj.poly)) )
-    error ("subscript out of range")
-  end
-
-  r = length(obj.poly);
+  r = length (obj.poly);
 
 endfunction
diff --git a/examples/@polynomial/subsasgn.m b/examples/@polynomial/subsasgn.m
--- a/examples/@polynomial/subsasgn.m
+++ b/examples/@polynomial/subsasgn.m
@@ -1,20 +1,31 @@
-function p = subsasgn (p, index, val)
-  index.type
-  index.subs
-  switch (index.type)
-    case "()"
-      ind = index.subs;
-      if ( (any (ind{:}>length(p.poly)))
-        || (any (ind{:}<0)) )
-        error ("subsasgn: subscript out of range");
+function p = subsasgn (p, s, val)
+  if (length (s) < 1)
+    error ("polynomial: needs index");
+  endif
+  switch (s(1).type)
+    case "{}"
+      ind = s(1).subs;
+      if (numel (ind) != 1)
+        error ("polynomial: need exactly one index");
+      else
+        if (length (s) == 1)
+          p.poly(ind{1}+1) = val;
+        else
+          error ("polynomial: chained subscripts not allowed for {}");
+        endif
       endif
-      p.poly(ind{:}) = val;
     case "."
-      fld = index.subs;
+      fld = s(1).subs;
       if (strcmp (fld, "poly"))
-        p.poly = val;
+        if (length (s) == 1)
+          p.poly = val;
+        else
+          p.poly = subsasgn (p.poly, s(2:end), val);
+        endif
       else
         error ("@polynomial/subsref: invalid property \"%s\"", fld);
       endif
+    otherwise
+      error ("invalid subscript type");
   endswitch
 endfunction
diff --git a/examples/@polynomial/subsref.m b/examples/@polynomial/subsref.m
--- a/examples/@polynomial/subsref.m
+++ b/examples/@polynomial/subsref.m
@@ -1,11 +1,22 @@
 function b = subsref (a, s)
-  switch s.type
+  if (isempty (s))
+    error ("polynomial: missing index");
+  endif
+  switch (s(1).type)
     case "()"
-      ind = s.subs;
-      b = polyval (fliplr(a.poly), ind{:});
+      ind = s(1).subs;
+      if (numel (ind) != 1)
+        error ("polynomial: need exactly one index");
+      else
+        b = polyval (fliplr (a.poly), ind{1});
+      endif
     case "{}"
-      ind = s.subs;
-      b = polynomial (a.poly(ind{:}));
+      ind = s(1).subs;
+      if (numel (ind) != 1)
+        error ("polynomial: need exactly one index");
+      else
+        b = a.poly(ind{1}+1);
+      endif
     case "."
       fld = s.subs;
       if (strcmp (fld, "poly"))
@@ -13,5 +24,10 @@
       else
         error ("@polynomial/subsref: invalid property \"%s\"", fld);
       endif
+    otherwise
+      error ("invalid subscript type");
   endswitch
+  if (numel (s) > 1)
+    b = subsref (b, s(2:end));
+  endif
 endfunction