%
% stack: value set-value event-name
%
% look upwards through the task tree selection lineage
%
"selev " _\ & log)(
!event
%
% find value socket upwards in tree
%
% default to current selection
%
 _event _\
%
% stack: value set-value event-name selected
%
"sel" log)(
 "Valued" get
 {
%
% for selected node value exists
%
  -1
 }
 {
%
% no value in selected node, move upwards to find prototype
%
  _\
  {
   Mep._Above
"up" log)(
   dup whole
   {
%
% there is a parent node, check for value exists
%
"sets" log)(
    _event second "Valued" get
_event ^"wh " log)(
    {
%
% value exists in ancestor node, this will be prototype
%
     dup !\ true
    }
    {
%
% not in this ancestor
%
     false
    } ifelse
   }
   {
%
% no more ancestral nodes
%
    true
   } ifelse
%
% stack: value set-value node stop-looking
%
   ?
  } loop

 } ifelse
 tuck
%
% stack: node value set-value
%
 {
%
% set the value in the current/ancestry socket 
% leave the prior version on the stack
%
  _event \_ exch _event \!
 }
 {
%
% get the value in the current/ancestry socket
%
  _event _\ "Valued" get
  {
   pop _event \_
  }
  {
%
% use supplied value
%
  } ifelse

 } ifelse

 exch negative

%
% stack: value was-current
%
% for setting value, resulting value is prior tree node value content
% if nothing returned for prior content, can use as prior existence flag
%