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Diffstat (limited to 'perl_checker.src/common.ml')
-rw-r--r-- | perl_checker.src/common.ml | 798 |
1 files changed, 798 insertions, 0 deletions
diff --git a/perl_checker.src/common.ml b/perl_checker.src/common.ml new file mode 100644 index 0000000..4b33f8f --- /dev/null +++ b/perl_checker.src/common.ml @@ -0,0 +1,798 @@ +open Stack +open List + +exception Found +exception Not_comparable +exception GraphSort_circular_deps + +type ('a, 'b) either = Left of 'a | Right of 'b +type ('a, 'b) or_option = Or_some of 'a | Or_error of 'b + +let bpos = "",-1,-1 + +let norm (a,b) = if a = -1 then b else a +let unipos (s,a,b) (s2,c,d) = + if (a,b) = (-1,-1) then s2,c,d else + if (c,d) = (-1,-1) then s,a,b else + if s <> s2 then bpos else s, min (norm(a,c)) (norm(c,a)), max (norm(b,d)) (norm(d,b)) + +let uniposl l = match l with + | [] -> bpos + | e::l -> fold_left unipos e l + +(**********************************************************************************) + +let internal_error s = failwith ("internal error: " ^ s) + +let id x = x +let double a = a,a +let swap (x,y) = (y,x) +let safe_tl l = try tl l with _ -> [] + +let o f g x = f (g x) +let curry f x y = f (x,y) +let uncurry f (x, y) = f x y + +let is_int n = ceil n = n + +let uncons = function + | [] -> failwith "uncons" + | e::l -> e,l + +let has_env var = + try + let _ = Sys.getenv var in true + with Not_found -> false + +let some = function Some e -> e | None -> failwith "some" + +let some_or = function + | None -> id + | Some e -> fun _ -> e + +let option2l = function + | None -> [] + | Some e -> [e] + +let prefer_some f a b = + match a, b with + | Some a, Some b -> Some (f a b) + | None, _ -> b + | _, None -> a + +let rec collect_accu f accu = function + | [] -> accu + | e::l -> collect_accu f (rev_append (f e) accu) l + +let collect f l = rev (collect_accu f [] l) + +let merge_some merge a b = + match a,b with + | None, None -> None + | _, None -> a + | None, _ -> b + | Some(a), Some(b) -> Some(merge a b) + +let rec uniq = function + | [] -> [] + | e::l -> if mem e l then uniq l else e :: uniq l + +let rec uniq_ eq = function + | [] -> [] + | e::l -> + try + let _ = find (eq e) l in + uniq_ eq l + with Not_found -> e :: uniq_ eq l + +let rec non_uniq = function + | [] -> [] + | e::l -> if mem e l then e :: non_uniq l else non_uniq l + +let rec member_ eq e = function + | [] -> false + | e'::l -> if eq e e' then true else member_ eq e l + +let rec find_some p = function + | [] -> raise Not_found + | x :: l -> + match p x with + | Some v -> v + | None -> find_some p l + +let fold_left1 f = function + | [] -> failwith "fold_left1" + | e :: l -> fold_left f e l + +let find_index e l = + let rec find_index_ i = function + | [] -> raise Not_found + | e'::l -> if e=e' then i else find_index_ (i+1) l + in + find_index_ 0 l + +let rec find_some_ p = function + | [] -> None + | x :: l -> + match p x with + | Some v -> Some v + | None -> find_some_ p l + +let rec fpartition p l = + let rec part yes no = function + | [] -> (rev yes, rev no) + | x :: l -> + (match p x with + | None -> part yes (x :: no) l + | Some v -> part (v :: yes) no l) in + part [] [] l + +let partition_either f l = + let rec part_either left right = function + | [] -> (rev left, rev right) + | x :: l -> + (match f x with + | Left e -> part_either (e :: left) right l + | Right e -> part_either left (e :: right) l) in + part_either [] [] l + +let rec keep_best f = + let rec partition e = function + | [] -> e, [] + | e' :: l -> + match f(e,e') with + | None -> let (e'', l') = partition e l in e'', e' :: l' + | Some e'' -> partition e'' l + in function + | [] -> [] + | e::l -> + let (e', l') = partition e l in + e' :: keep_best f l' + +let rec keep_bests f l = + let rec once e unchanged = function + | [] -> None + | e' :: l -> + match f(e,e') with + | None -> once e (e' :: unchanged) l + | Some e'' -> Some(e'', unchanged @ l) + in + let rec as_many_as_possible e l = + match once e [] l with + | None -> None + | Some(e', l') -> Some(some_or (as_many_as_possible e' l') (e', l')) + in + let rec try_with e l_done l_next = + match as_many_as_possible e l_next with + | None -> try_with_next (e :: l_done) l_next + | Some(e2, l_next2) -> + match as_many_as_possible e2 l_done with + | None -> try_with_next (e2 :: l_done) l_next2 + | Some(e3, l_done2) -> try_with e3 l_done2 l_next2 + and try_with_next l_done = function + | [] -> rev l_done + | e::l_next -> try_with e l_done l_next + in + try_with_next [] l + +let rec fold_right1 f = function + | [] -> failwith "fold_right1" + | [e] -> e + | e::l -> f e (fold_right1 f l) + +let rec for_all2_ p l1 l2 = + match (l1, l2) with + ([], []) -> true + | (a1::l1, a2::l2) -> p a1 a2 && for_all2_ p l1 l2 + | (_, _) -> false + +let maxl l = fold_right1 max l + +let rec stack2list s = + let l = ref [] in + Stack.iter (fun e -> l := e :: !l) s ; + !l + +let rec fix_point f p = + let p' = f p in + if p = p' then p else fix_point f p' + +let rec fix_point_withenv f env p = + let p', env' = f env p in + if p = p' then (p, env') else fix_point_withenv f env' p' + +let rec fix_point_ nb f p = + let p' = f p in + if p = p' then p, nb else fix_point_ (nb+1) f p' + +(* +let rec lfix_point f e = + let e' = f(e) in + if e = e' then e :: lfix_point f e' else [e] +*) + +let do0_withenv doit f env l = + let r_env = ref env in + doit (fun e -> r_env := f !r_env e) l ; + !r_env + +let do0_withenv2 doit f env l = + let r_env = ref env in + doit (fun e e' -> r_env := f !r_env e e') l ; + !r_env + +let do_withenv doit f env l = + let r_env = ref env in + let l' = doit (fun e -> + let e', env' = f !r_env e in + r_env := env' ; e' + ) l in + l', !r_env + +let do2_withenv doit f env l1 l2 = + let r_env = ref env in + let l' = doit (fun e1 e2 -> + let e', env' = f !r_env e1 e2 in + r_env := env' ; e' + ) l1 l2 in + l', !r_env + +let do_collect doit f l1 = + let l = ref [] in + doit (fun i t -> l := f i t @ !l) l1 ; + !l + +let map_withitself f l = + let rec map_withitself_ done_ = function + | [] -> done_ + | e :: l -> + let e' = f (done_ @ e :: l) e in + map_withitself_ (done_ @ [ e' ]) l + in map_withitself_ [] l + +let map_t2 f (x,y) = f x, f y +let map_t3 f (x,y,z) = f x, f y, f z +let map_option f = function + | Some e -> Some (f e) + | None -> None +let map_optionoption f = function + | Some e -> f e + | None -> None +let t2_option2option_t2 = function + | (Some x, Some y) -> Some(x,y) + | _ -> None +let rec l_option2option_l = function + | [] -> Some [] + | None :: _l -> None + | Some e :: l -> map_option (fun l -> e :: l) (l_option2option_l l) +let map_option_env f (e, env) = map_option f e, env + +let if_some bool val_ = if bool then Some val_ else None + +let rec fold_left_option f val_ = function + | [] -> Some val_ + | e::l -> + match f val_ e with + | None -> None + | Some val_' -> fold_left_option f val_' l + +let collect_some_withenv f env l = + let rec collect accu env = function + | [] -> rev accu, env + | e::l -> + let e', env' = f env e in + let accu' = + match e' with + | Some e' -> e'::accu + | None -> accu in + collect accu' env' l + in collect [] env l + +let for_all_option_withenv remap f env l = + let rec for_all env accu = function + | [] -> Some(remap (rev accu)), env + | e::l -> + (match f env e with + | None, env' -> None, env' + | Some e', env' -> for_all env' (e' :: accu) l) + in + for_all env [] l + +let for_all2_option_withenv remap f env la lb = + let rec for_all env accu = function + | [], [] -> Some(remap (rev accu)), env + | a::la, b::lb -> + (match f env a b with + | None, env' -> None, env' + | Some ab, env' -> for_all env' (ab :: accu) (la, lb)) + | _ -> None, env + in + for_all env [] (la, lb) + +let map_or_option f = function + | Or_some e -> Or_some (f e) + | Or_error err -> Or_error err + +let map_index f l = + let rec map_ n = function + | [] -> [] + | e::l -> f e n :: map_ (n+1) l + in map_ 0 l + +let filter_index f l = + let rec filter_ n = function + | [] -> [] + | e::l -> + let l' = filter_ (n+1) l in + if f e n then e :: l' else l' + in filter_ 0 l + +let iter_index f l = + let rec iter_ n = function + | [] -> () + | e::l -> f e n ; iter_ (n+1) l + in iter_ 0 l + +let map_fst f (x, y) = f x, y +let map_snd f (x, y) = x, f y + +let map_withenv f env e = do_withenv map f env e +let find_withenv f env e = do_withenv find f env e +let filter_withenv f env e = do_withenv filter f env e +let exists_withenv f env e = do_withenv exists f env e +let map_t2_withenv f env e = do_withenv map_t2 f env e +let for_all_withenv f env e = do_withenv for_all f env e +let collect_withenv f env e = do_withenv collect f env e +let partition_either_withenv f env e = do_withenv partition_either f env e + +let map2_withenv f env l1 l2 = do2_withenv map2 f env l1 l2 +let for_all2_withenv f env l1 l2 = do2_withenv for_all2 f env l1 l2 + +let rec take n l = + if n = 0 then [] + else match l with + | [] -> raise Not_found + | e::l -> e :: take (n-1) l +let last_n n l = rev (take n (rev l)) +let last l = hd (last_n 1 l) + +let rec skipfirst e = function + | [] -> [] + | e'::l when e = e' -> skipfirst e l + | l -> l + +let rec removelast = function + | [] -> failwith "removelast" + | [_] -> [] + | e::l -> e :: removelast l + +let rec split_last l = + let rec spl accu = function + | [] -> failwith "split_last" + | [e] -> rev accu, e + | e::l -> spl (e :: accu) l + in spl [] l + +let iter_assoc_val f l = iter (fun (_,v) -> f v) l +let map_assoc_val f l = map (fun (k,v) -> k, f v) l + +let assoc_or_fail e l = + try assoc e l with Not_found -> failwith "assoc failed" + +let assoc_has_key e l = + try let _ = assoc e l in true with Not_found -> false + +let assoc_by is_same e l = + find_some (fun (a,b) -> if is_same e a then Some b else None) l + +let rec update_assoc_by is_same f e = function + | [] -> raise Not_found + | (a,b) :: l when is_same e a -> (a, f b) :: l + | (a,b) :: l -> (a,b) :: update_assoc_by is_same f e l + +let update_assoc f e = update_assoc_by (=) f e + +let rec update_assoc_by_with_default default is_same f e = function + | [] -> [ e, f default ] + | (a,b) :: l when is_same e a -> (a, f b) :: l + | (a,b) :: l -> (a,b) :: update_assoc_by_with_default default is_same f e l + +let update_all_assoc_by is_same f e l = + map (fun (a,b) -> a, if is_same e a then f b else b) l + +let rec rassoc e = function + | [] -> raise Not_found + | (k,v) :: l -> if e = v then k else rassoc e l + +let rec all_assoc e = function + | [] -> [] + | (e',v) :: l when e=e' -> v :: all_assoc e l + | _ :: l -> all_assoc e l + +let rec all_assoc_by is_same e = function + | [] -> [] + | (e',v) :: l when is_same e e' -> v :: all_assoc_by is_same e l + | _ :: l -> all_assoc_by is_same e l + +let prepare_want_all_assoc l = + map (fun n -> n, uniq (all_assoc n l)) (uniq (map fst l)) + +let prepare_want_all_assoc_by is_same l = + map (fun n -> n, uniq_ is_same (all_assoc_by is_same n l)) (uniq_ is_same (map fst l)) + +let prepare_want_all_assoc_by_ is_same_a is_same_b l = + map (fun n -> n, uniq_ is_same_b (all_assoc_by is_same_a n l)) (uniq_ is_same_a (map fst l)) + +let rec count_uniq = function + | [] -> [] + | e::l -> + let has, l' = partition ((=) e) l in + (e, length has + 1) :: count_uniq l' + +let rec repeat e = function + | 0 -> [] + | n -> e :: repeat e (n-1) + +let rec inits = function + | [] -> [[]] + | e::l -> [] :: map (fun l -> e::l) (inits l) +let rec tails = function + | [] -> [[]] + | (_::xs) as xxs -> xxs :: tails xs + +let apply f x = f x;; + +let rec map3 f l1 l2 l3 = + match (l1, l2, l3) with + ([], [], []) -> [] + | (a1::l1, a2::l2, a3::l3) -> let r = f a1 a2 a3 in r :: map3 f l1 l2 l3 + | (_, _, _) -> invalid_arg "map3" + +let filter2 f l1 l2 = + split (filter f (combine l1 l2)) + +let break_at f l = + let rec b l1 = function + | [] -> l1, [] + | e::l2 -> if f e then (l1, e :: l2) else b (l1 @ [e]) l2 + in b [] l +let break v l = break_at ((=) v) l + +(* break_at_indice 0 [1;2] gives [], [1;2] + break_at_indice 1 [1;2] gives [1], [2] + *) +let rec break_at_indice i l = + if i = 0 then [], l else + match l with + | [] -> raise Not_found + | e::l2 -> + let a, b = break_at_indice (i-1) l2 in + e::a, b + +let rev_nth e l = + let rec rev_nth' i = function + | [] -> raise Not_found + | e'::_ when e'=e -> i + | _::l -> rev_nth' (i+1) l + in rev_nth' 0 l + +let rec getset_nth l i f = + match l, i with + | e::l', 0 -> f e :: l' + | [], _ -> failwith "getset_nth" + | e::l', _ -> e :: getset_nth l' (i - 1) f + +let set_nth l i v = getset_nth l i (fun _ -> v) + +let adjustModDown m n = n - (n mod m) +let adjustModUp m n = adjustModDown m (n + m - 1) + + +let hashtbl_set h k v = + Hashtbl.remove h k; + Hashtbl.add h k v + +let hashtbl_find f h = + let r = ref None in + Hashtbl.iter (fun v c -> if f v c then r := Some v) h ; + match !r with + | Some v -> v + | None -> raise Not_found + +let hashtbl_filter f h = + Hashtbl.iter (fun v c -> hashtbl_set h v (f v c)) h + +let array_shift a = Array.sub a 1 (Array.length a - 1) +let array_last_n n a = + let len = Array.length a in + Array.sub a (len - n) n + +let array_collect f a = Array.fold_left (fun l e -> f e @ l) [] a + +let rec lvector_product = + let rec vector_product a b = match a with + | [] -> [] + | e::l -> map (fun e' -> e :: e') b :: vector_product l b + in function + | [] -> [] + | [e] -> map (fun e -> [e]) e + | e::l -> flatten (vector_product e (lvector_product l)) + +let vector_product2 a b = + map (function + | [a;b] -> a,b + | _ -> failwith "vector_product2" + ) (lvector_product [ a ; b ]) + +let rec transpose = function + | [] :: _ -> [] + | ll -> + let l, ll' = split (map (function e::l -> e,l | _ -> raise Not_found) ll) in + l :: transpose ll' + +let rec range min max = + if min >= max then [] else min :: range (min + 1) max + +let rec filter_some_with f = function + | [] -> [] + | e :: l -> + match f e with + | None -> filter_some_with f l + | Some e' -> e' :: filter_some_with f l + +let rec filter_some = function + | [] -> [] + | None :: l -> filter_some l + | Some e :: l -> e :: filter_some l + +let rec difference l = function + | [] -> l + | e::l' -> difference (filter ((<>) e) l) l' + +let rec difference_ eq l = function + | [] -> l + | e::l' -> + let l2 = filter (fun e' -> not (eq e e')) l in + difference_ eq l2 l' + +let intersection_by is_same l1 l2 = filter (fun e -> exists (is_same e) l2) l1 + +let intersection_and_differences eq l1 l2 = + let rec both inter l2_only = function + | [], l2 -> inter, [], rev l2_only @ l2 + | l1, [] -> inter, l1, rev l2_only + | l1, e2 :: l2' -> + match partition (eq e2) l1 with + | [], _ -> both inter (e2 :: l2_only) (l1, l2') + | _, l1' -> both (e2 :: inter) l2_only (l1', l2') + in both [] [] (l1, l2) + +let rec triangularize = function + | [] -> [] + | e::l -> (e,l) :: triangularize l + +let diagonalize l = + map_index (fun a i -> + a, filter_index (fun _ j -> i <> j) l + ) l + +let rec list_of_nonempty_sublists = function + | [] -> [] + | e :: l -> + let l' = list_of_nonempty_sublists l in + [e] :: l' @ map (fun l -> e :: l) l' + +let rec graph_is_sorted_by eq = function + | [] -> true + | (_,deps) :: l -> + for_all (fun e -> try let _ = assoc_by eq e l in false with Not_found -> true) deps && graph_is_sorted_by eq l + +let graph_closure_by eq graph = + let err = ref None in + try + let graph_rev = collect (fun (i, l) -> map (fun e -> (e, i)) l) graph in + let bothway = map (fun (i,l) -> i, (l, all_assoc_by eq i graph_rev)) graph in + let closed = fold_left (fun graph j -> + let next, prev = assoc_by eq j graph in + let graph2 = fold_left (fun graph i -> + if member_ eq i next then (err := Some(j,i); raise GraphSort_circular_deps) else + update_assoc_by eq (fun (i_next,i_prev) -> i_next @ next, i_prev) i graph + ) graph (filter (fun a -> not (eq a j)) prev) in + let graph3 = fold_left (fun graph k -> + if member_ eq k prev then (err := Some(j,k); raise GraphSort_circular_deps) else + update_assoc_by eq (fun (k_next,k_prev) -> k_next, k_prev @ prev) k graph + ) graph2 (filter (fun a -> not (eq a j)) next) in + graph3 + ) bothway (map fst bothway) in + Or_some (map (fun (e,(next,_)) -> e, uniq_ eq next) closed) + with GraphSort_circular_deps -> + Or_error (some !err) + +let rec graph_sort_by eq l = + let cmp (_, deps_a) (b, _) = if member_ eq b deps_a then 1 else -1 in + let rec sort_it = function + | [] -> [] + | [e] -> [e] + | e::l -> + let l' = sort_it l in + let gt, lt = break_at (fun ((_, deps) as e') -> deps = [] or cmp e e' = 1) l' in + gt @ [e] @ lt + in + map_or_option (fun l' -> + let l_sorted = rev (sort_it l') in + if not (graph_is_sorted_by eq l_sorted) then internal_error "graph_sort failed" else + l_sorted + ) (graph_closure_by eq l) + +let int_sort l = sort (fun a b -> a - b) l + +let str_begins_with s prefix = + String.sub s 0 (min (String.length s) (String.length prefix)) = prefix + +let rec str_contains s1 s2 = + match s1 with + | "" -> false + | _ -> + if str_begins_with s1 s2 then true + else str_contains (String.sub s1 1 (String.length s1 - 1)) s2 + +let str_ends_with s suffix = + let len = min (String.length s) (String.length suffix) in + String.sub s (String.length s - len) len = suffix + +let chop = function + | "" -> "" + | s -> String.sub s 0 (String.length s - 1) + +let chomps s = + let i = ref (String.length s - 1) in + while !i >= 0 && (s.[!i] = ' ' || s.[!i] = '\t') do decr i done ; + String.sub s 0 (!i+1) + +let skip_n_char_ beg end_ s = + String.sub s beg (String.length s - beg - end_) +let skip_n_char n s = skip_n_char_ n 0 s + +let rec explode_string = function + | "" -> [] + | s -> (String.get s 0) :: explode_string (String.sub s 1 (String.length s - 1)) + +let is_uppercase c = Char.lowercase c <> c +let is_lowercase c = Char.uppercase c <> c + +let starts_with_non_lowercase s = s <> "" && s.[0] <> '_' && not (is_lowercase s.[0]) + +let get_package_name s = + try Some (String.sub s 0 (String.rindex s ':' - 1)) with Not_found -> None + +let split_at_two_colons s = + let i_fq = String.rindex s ':' in + String.sub s 0 (i_fq - 1), skip_n_char (i_fq + 1) s + +let to_CamelCase s_ = + let l = ref [] in + let s = String.copy s_ in + for i = 1 to String.length s - 1 do + if is_uppercase (String.unsafe_get s i) && is_lowercase (String.unsafe_get s (i-1)) then ( + String.set s i (Char.lowercase (String.get s i)) ; + l := i :: !l + ) + done ; + if !l = [] then None else + let offset, s' = fold_left (fun (offset, s') i -> + i, s' ^ String.sub s offset (i-offset) ^ "_" + ) (0, "") (rev !l) in + Some (s' ^ String.sub s offset (String.length s - offset)) + +let (string_of_ref : 'a ref -> string) = fun r -> + Printf.sprintf "0x%x" (Obj.magic r : int) + +let is_int n = n = floor n + +(* total order *) +let rec compare_lists cmp l1 l2 = + match l1, l2 with + | [], [] -> 0 + | [], _ -> -1 + | _, [] -> 1 + | e1::l1, e2::l2 -> + match cmp e1 e2 with + | 0 -> compare_lists cmp l1 l2 + | v -> v + +let compare_best a b = + match a, b with + | 0, 0 -> 0 + | 1, 1 | 1, 0 | 0, 1 -> 1 + | -1, -1 | -1, 0 | 0, -1 -> -1 + | 1, -1 | -1, 1 -> raise Not_comparable + | _ -> failwith "uh?" + +(* partial order *) +let combine_comparison_list l = + fold_left compare_best 0 l + +let min_with_cmp less_than a b = + if less_than a b then a + else if less_than b a then b + else raise Not_comparable + +let max_with_cmp less_than a b = + if less_than a b then b + else if less_than b a then a + else raise Not_comparable + +let rec fold_left2_compare f e l1 l2 = + match l1, l2 with + | [], [] -> e + | e1::l1, e2::l2 -> fold_left2_compare f (f e e1 e2) l1 l2 + | _ -> raise Not_comparable + +let rec exists_compare cmp = function + | [] -> raise Not_comparable + | e :: l -> try cmp e with Not_comparable -> exists_compare cmp l + +let forall_compare cmp = fold_left (fun n e -> compare_best n (cmp e)) 0 +let forall2_compare cmp = fold_left2_compare (fun n e1 e2 -> compare_best n (cmp e1 e2)) 0 + +let exists2_compare left_dropping cmp l1 l2 = + let rec forall_compare_ n = function + | [], [] -> n + | _, [] -> compare_best n left_dropping + | [], _ -> compare_best n (-left_dropping) + | e1::l1, e2::l2 -> + match try Some (cmp e1 e2) with Not_comparable -> None with + | Some n' -> forall_compare_ (compare_best n n') (l1, l2) + | None -> + if n = left_dropping then + forall_compare_ left_dropping (l1, e2::l2) + else if n = -left_dropping then + forall_compare_ (-left_dropping) (e1::l1, l2) + else + (* need to try both *) + try forall_compare_ left_dropping (l1, e2::l2) + with Not_comparable -> forall_compare_ (-left_dropping) (e1::l1, l2) + in forall_compare_ 0 (l1, l2) + + +let rec compare_sorted_sets is_same l1 l2 = + match l1, l2 with + | [], [] -> 0 + | [], _ -> -1 + | _, [] -> 1 + | e1::l1, e2::l2 -> if is_same e1 e2 then compare_sorted_sets is_same l1 l2 else raise Not_found + +let scan_list_while_modifying f l = + let rec scan_list_while_modifying_ prev = function + | [] -> prev + | e :: next -> + let prev', next' = some_or (f prev next e) (prev @ [e], next) in + scan_list_while_modifying_ prev' next' + in scan_list_while_modifying_ [] l + +let bools2compare = function + | true, true -> 0 + | true, false -> -1 + | false, true -> 1 + | _ -> raise Not_comparable + +let lpush l e = l := e :: !l + +(* +let is_greater2compare is_greater a b = + match is_greater a b, is_greater b a with + + *) + +module OrderedString = + struct + type t = string + let compare = compare + end;; + +module StringSet = Set.Make(OrderedString);; + +let stringSet_to_list = StringSet.elements +let stringSet_add set e = StringSet.add e set +let stringSet_difference = StringSet.diff +let list_to_StringSet l = fold_left stringSet_add StringSet.empty l |