treefun* functions support variable output arguments

@tree/treefun.m

@@ -1,16 +1,36 @@
-function newTree = treefun(obj, fun)
+function varargout = treefun(obj, fun)
 %% TREEFUN  Create a new tree by applying function handle to each node of the source tree.
-
     if ~isa(fun, 'function_handle')
         error('MATLAB:tree:treefun', ...
             'Second argument, fun, must be a function handle. Got a %s.', ...
             class(fun));
     end
-
-    % First we copy
-    newTree = tree(obj, 'clear'); 
-
-    % Then we override
-    newTree.Node = cellfun(fun, obj.Node, 'UniformOutput', false);
-
+    % validate number of output arguments is <= # outputs of `fun`
+    nargoutchk(0,abs(nargout(fun)));
+
+    % if called interactively, nargout=0, which causes problems in `cellfun`
+    % given: 
+    % >> t
+    % t = ...
+    %   Node: {3x1 cell}
+    % e.g. if this isn't done...
+    % >> t.treefun(@(x) x+1)
+    % >>
+    % but by setting output number to 1, `ans` will be assigned
+    % >> t.treefun(@(x) x+1);
+    % ans = ...
+    %   Node: {3x1 cell}
+    if ~nargout
+        n_out = 1;                      % need new variable b/c can't
+                                        % reassign nargout
+    else
+        n_out = nargout;
+    end
+
+    % cellfun call collects output into n_outx1 cell array
+    [nodes{1:n_out}] = cellfun(fun,obj.Node,'UniformOutput',false);
+    for k = 1:n_out                     % copy each output to its own tree
+        varargout{k} = tree(obj,'clear');
+        varargout{k}.Node = nodes{k};
+    end
 end

@tree/treefun2.m

@@ -1,19 +1,32 @@
-function obj = treefun2(obj, val, fun)
+function varargout = treefun2(obj, val, fun)
 %%TREEFUN2  Two-arguments function on trees, with scalar expansion.
+    if ~isa(fun, 'function_handle')
+        error('MATLAB:tree:treefun', ...
+            'Second argument, fun, must be a function handle. Got a %s.', ...
+            class(fun));
+    end
+    nargoutchk(0,abs(nargout(fun)));    % validate # output args
 
     [obj, val] = permuteIfNeeded(obj, val);
 
-     if isa(val, 'tree')
-
-        content = cellfun(fun, obj.Node, val.Node, ...
-            'UniformOutput', false);
+    % if nargout = 0, set it to 1 so that `ans` is assigned 
+    % (see comment in `treefun.m`)
+    if ~nargout, n_out = 1; else n_out = nargout; end
+
+    if isa(val, 'tree')
 
-     else
-
-         content = cellfun(@(x) fun(x, val), obj.Node, ...
-            'UniformOutput', false);
+        [content{1:n_out}] = cellfun(fun, obj.Node, val.Node,...
+                                     'UniformOutput',false);
 
-     end
+    else
+
+        [content{1:n_out}] = cellfun(@(x) fun(x, val), obj.Node, ...
+                                     'UniformOutput', false);
+
+    end
 
-     obj.Node = content;
+    for k = 1:n_out
+        varargout{k} = tree(obj,'clear');
+        varargout{k}.Node = content{k};
+    end
 end