docs: function(ast, source) {
        if(!ast) return;
        for(var i=0;i<ast.length;i++) {
          var node=ast[i];
          if(node && node.length>=3 && node[0]=='=') {
            // looking for ['=', id, val]
            runtime.ast()[node[1]] = {'ast': [node]};
            runtime.source()[node[1]] = source;
          }
        }
      }