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|
(* camlp5r *)
(* extfun.ml,v *)
(* Copyright (c) INRIA 2007-2017 *)
(* Extensible Functions *)
type ('a, 'b) t = ('a, 'b) matching list
and ('a, 'b) matching = { patt : patt; has_when : bool; expr : ('a, 'b) expr }
and patt =
Eapp of patt list
| Eacc of patt list
| Econ of string
| Estr of string
| Eint of string
| Etup of patt list
| Erec of (patt * patt) list
| Evar of unit
and ('a, 'b) expr = 'a -> 'b option;;
exception Failure;;
let empty = [];;
(*** Apply ***)
let rec apply_matchings a =
function
m :: ml ->
begin match m.expr a with
None -> apply_matchings a ml
| x -> x
end
| [] -> None
;;
let apply ef a =
match apply_matchings a ef with
Some x -> x
| None -> raise Failure
;;
(*** Trace ***)
let rec list_iter_sep f s =
function
[] -> ()
| [x] -> f x
| x :: l -> f x; s (); list_iter_sep f s l
;;
let rec print_patt =
function
Eapp pl -> list_iter_sep print_patt2 (fun () -> print_string " ") pl
| p -> print_patt2 p
and print_labeled_patt_pair (p1, p2) =
print_patt p1; print_string " = "; print_patt p2
and print_patt2 =
function
Eacc pl -> list_iter_sep print_patt1 (fun () -> print_string ".") pl
| p -> print_patt1 p
and print_patt1 =
function
Econ s -> print_string s
| Estr s -> print_string "\""; print_string s; print_string "\""
| Eint s -> print_string s
| Evar () -> print_string "_"
| Etup pl ->
print_string "(";
list_iter_sep print_patt (fun () -> print_string ", ") pl;
print_string ")"
| Erec l ->
print_string "{";
list_iter_sep print_labeled_patt_pair (fun () -> print_string "; ") l;
print_string "}"
| Eapp _ | Eacc _ as p -> print_string "("; print_patt p; print_string ")"
;;
let print ef =
List.iter
(fun m ->
print_patt m.patt;
if m.has_when then print_string " when ...";
print_newline ())
ef
;;
(*** Extension ***)
let compare_patt p1 p2 =
match p1, p2 with
Evar _, _ -> 1
| _, Evar _ -> -1
| _ -> compare p1 p2
;;
let insert_matching matchings (patt, has_when, expr) =
let m1 = {patt = patt; has_when = has_when; expr = expr} in
let rec loop =
function
m :: ml as gml ->
if m1.has_when && not m.has_when then m1 :: gml
else if not m1.has_when && m.has_when then m :: loop ml
else
let c = compare_patt m1.patt m.patt in
if c < 0 then m1 :: gml
else if c > 0 then m :: loop ml
else if m.has_when then m1 :: gml
else m1 :: ml
| [] -> [m1]
in
loop matchings
;;
(* available extension function *)
let extend ef matchings_def =
List.fold_left insert_matching ef matchings_def
;;
|
