(*
    ocamlc -pp "camlp4o pa_extend.cmo q_MLast.cmo" -I +camlp4 -c syntax1.ml
*)

open Pcaml;;

EXTEND
    str_item: LAST
	[[ EOI -> assert false
	| "WHERE" -> <:str_item< $lid:"wHERE"$ >> ]];
END;;

(* generally, this splits a list, then reverses the large parts
    and concat  them back *)
let wrap f x = 
    let split pred l =
    (* cound not found it *)
	let rec s1 rl add argl = 
	    try let e = List.hd argl
		and tl = List.tl argl in
		match (pred e,add,rl)
		    with (false,true,rl) -> s1 ([e]::rl) false tl
		    | (false,false,re::rl') -> s1 ((e::re)::rl') false tl
		    | (false,false,[]) -> assert false
		    | (true,false,rl) -> s1 rl true tl
		    | (true,true,rl) -> s1 ([]::rl) true tl
	    with Failure "hd" | Failure "tl" -> rl
	in
	s1 [] true l in
    let wrapV (l,fl) =
	let m1 = function (<:str_item< $lid:"wHERE"$ >>,_) -> true
			| _ -> false in
	let (&>) f1 f2 x = f2 (f1 x) in
	let res = (split m1 &> List.map List.rev &> List.concat) l in
	(res,fl) in
    wrapV (f x);;

Pcaml.parse_implem := wrap (!Pcaml.parse_implem);;