Returns a node list containing all the nodes from nodelist whose GIs are NOT members of gilist. The order of nodes in the node list is preserved.
(define (node-list-filter-by-not-gi nodelist gilist)
;; Returns selected elements from a node list
(let loop ((result (empty-node-list)) (nl nodelist))
(if (node-list-empty? nl)
result
(if (member (gi (node-list-first nl)) gilist)
(loop result (node-list-rest nl))
(loop (node-list result (node-list-first nl))
(node-list-rest nl))))))