backport some functions added in 4.05 in CCList

_tags

@@ -157,7 +157,7 @@ true: annot, bin_annot
 <src/threads/*.ml{,i}>: thread
 <src/core/CCVector.cmx> or <src/core/CCString.cmx>: inline(25)
 <src/data/CCFlatHashtbl.cm*> or <src/data/CCHashTrie.cm*> or <src/data/CCPersistent*>: inline(15)
-<src/core/CCMap.*> or <src/core/CCSet.*>: warn(-32)
+<src/core/CCMap.*> or <src/core/CCSet.*> or <src/core/CCList.*>: warn(-32)
 <src/**/*.ml> and not <src/misc/*.ml>: warn(+a-4-44-58-60@8)
 true: no_alias_deps, safe_string, short_paths
 <src/**/*Labels.cm*>: nolabels

src/core/CCList.ml

@@ -9,6 +9,53 @@
 
 type 'a t = 'a list
 
+(* backport new functions from stdlib here *)
+
+let nth_opt l n =
+  if n<0 then invalid_arg "nth_opt";
+  let rec aux l n = match l, n with
+    | [], _ -> None
+    | x::_, 0 -> Some x
+    | _::l, _ -> aux l (n-1)
+  in
+  aux l n
+
+(*$Q
+  Q.(pair small_nat (list int)) (fun (i,l) -> \
+    nth_opt l i = get_at_idx i l)
+*)
+
+let rec find_opt p l = match l with
+  | [] -> None
+  | x :: _ when p x -> Some x
+  | _ :: tl -> find_opt p tl
+
+let rec compare_lengths l1 l2 = match l1, l2 with
+  | [], [] -> 0
+  | [], _::_ -> 1
+  | _::_, [] -> -1
+  | _::tail1, _::tail2 -> compare_lengths tail1 tail2
+
+(*$Q
+  Q.(pair (list int) (list int)) (fun (l1,l2) -> \
+    CCOrd.equiv (compare_lengths l1 l2) \
+      (Pervasives.compare (length l1)(length l2)))
+*)
+
+let rec compare_length_with l n = match l, n with
+  | _ when n<0 -> -1
+  | [], 0 -> 0
+  | [], _ -> 1
+  | _::tail, _ -> compare_length_with tail (n-1)
+
+(*$Q
+  Q.(pair (list int) small_nat) (fun (l,n) -> \
+    CCOrd.equiv (compare_length_with l n) \
+      (Pervasives.compare (length l)n))
+*)
+
+(* end of backport *)
+
 include List
 
 let empty = []
@@ -802,10 +849,7 @@ let rec last_opt = function
   None (last_opt [])
 *)
 
-let rec find_pred p l = match l with
-  | [] -> None
-  | x :: _ when p x -> Some x
-  | _ :: tl -> find_pred p tl
+let find_pred = find_opt
 
 let find_pred_exn p l = match find_pred p l with
   | None -> raise Not_found

src/core/CCList.mli

@@ -97,6 +97,14 @@ val split : ('a * 'b) t -> 'a t * 'b t
 
 val compare : ('a -> 'a -> int) -> 'a t -> 'a t -> int
 
+val compare_lengths : 'a t -> 'b t -> int
+(** equivalent to [compare (length l1) (length l2)] but more efficient.
+    @since NEXT_RELEASE *)
+
+val compare_length_with : 'a t -> int -> int
+(** equivalent to [compare (length l) x] but more efficient.
+    @since NEXT_RELEASE *)
+
 val equal : ('a -> 'a -> bool) -> 'a t -> 'a t -> bool
 
 val flat_map : ('a -> 'b t) -> 'a t -> 'b t
@@ -225,6 +233,10 @@ val find_pred : ('a -> bool) -> 'a t -> 'a option
     or returns [None] if no element satisfies [p]
     @since 0.11 *)
 
+val find_opt : ('a -> bool) -> 'a t -> 'a option
+(** Safe version of {!find}
+    @since NEXT_RELEASE *)
+
 val find_pred_exn : ('a -> bool) -> 'a t -> 'a
 (** Unsafe version of {!find_pred}
     @raise Not_found if no such element is found
@@ -324,6 +336,11 @@ val foldi : ('b -> int -> 'a -> 'b) -> 'b -> 'a t -> 'b
 
 val get_at_idx : int -> 'a t -> 'a option
 
+val nth_opt : 'a t -> int -> 'a option
+(** Safe version of {!nth}.
+    @raise Invalid_argument if the int is negative.
+    @since NEXT_RELEASE *)
+
 val get_at_idx_exn : int -> 'a t -> 'a
 (** Get the i-th element, or
     @raise Not_found if the index is invalid *)
@@ -432,6 +449,14 @@ module Assoc : sig
       @since 0.17 *)
 end
 
+val assoc_opt : 'a -> ('a * 'b) t -> 'b option
+(** Safe version of {!assoc}
+    @since NEXT_RELEASE *)
+
+val assq_opt : 'a -> ('a * 'b) t -> 'b option
+(** Safe version of {!assq}
+    @since NEXT_RELEASE *)
+
 (** {2 References on Lists}
     @since 0.3.3 *)