nuop_new()
instantiates a newnuop
node.nuop_type()
checks if the node is anuop
node.nuop_<child>_get()
returns the<child>
node ofnuop
.nuop_<child>_set()
sets the new<child>
and deletes the old<child>
.nuop_<child>_rep()
sets the new<child>
and returns the old<child>
.