CCArray(feat): Add max,argmax,min,argmin and their _exn conterpart

src/core/CCArray.ml

@@ -153,6 +153,60 @@ let find_idx p a =
         None)
     a 0
 
+let max cmp a =
+  if Array.length a = 0 then None
+  else Some (
+      fold
+        (fun acc elt -> if cmp acc elt < 0 then elt else acc)
+        a.(0)
+        a)
+
+let max_exn cmp a =
+  match max cmp a with
+    | None -> invalid_arg __FUNCTION__
+    | Some elt -> elt
+
+
+let argmax cmp a =
+  if Array.length a = 0 then None
+  else Some (
+      foldi
+        (fun acc i elt -> if cmp a.(acc) elt < 0 then i else acc)
+        0
+        a)
+
+let argmax_exn cmp a =
+  match argmax cmp a with
+    | None -> invalid_arg __FUNCTION__
+    | Some elt -> elt
+
+let min cmp a =
+  if Array.length a = 0 then None
+  else Some (
+      fold
+        (fun acc elt -> if cmp acc elt > 0 then elt else acc)
+        a.(0)
+        a)
+
+let min_exn cmp a =
+  match min cmp a with
+    | None -> invalid_arg __FUNCTION__
+    | Some elt -> elt
+
+
+let argmin cmp a =
+  if Array.length a = 0 then None
+  else Some (
+      foldi
+        (fun acc i elt -> if cmp a.(acc) elt > 0 then i else acc)
+        0
+        a)
+
+let argmin_exn cmp a =
+  match argmin cmp a with
+    | None -> invalid_arg __FUNCTION__
+    | Some elt -> elt
+
 let filter_map f a =
   let rec aux acc i =
     if i = Array.length a then (
@@ -275,7 +329,7 @@ let rec _exists2 p a1 a2 i1 i2 ~len =
   && (p a1.(i1) a2.(i2) || _exists2 p a1 a2 (i1 + 1) (i2 + 1) ~len:(len - 1))
 
 let exists2 p a b =
-  _exists2 p a b 0 0 ~len:(min (Array.length a) (Array.length b))
+  _exists2 p a b 0 0 ~len:(Stdlib.min (Array.length a) (Array.length b))
 
 let _fold2 f acc a b i j ~len =
   let rec aux acc o =

src/core/CCArray.mli

@@ -142,6 +142,47 @@ val find_idx : ('a -> bool) -> 'a t -> (int * 'a) option
     and [f x] holds. Otherwise returns [None].
     @since 0.3.4 *)
 
+val max : ('a -> 'a -> int) -> 'a t -> 'a option
+(** [max cmp a] returns [None] if [a] is empty, otherwise, returns [Some e] where [e]
+    is a maximum element in [a] with respect to [cmp].
+    @since NEXT_RELEASE *)
+
+val max_exn : ('a -> 'a -> int) -> 'a t -> 'a
+(** [max_exn cmp a] is like {!max}, but
+    @raise Invalid_argument if [a] is empty.
+    @since NEXT_RELEASE *)
+
+
+val argmax : ('a -> 'a -> int) -> 'a t -> int option
+(** [argmax cmp a] returns [None] if [a] is empty, otherwise, returns [Some i] where [i]
+    is the index of a maximum element in [a] with respect to [cmp].
+    @since NEXT_RELEASE *)
+
+val argmax_exn : ('a -> 'a -> int) -> 'a t -> int
+(** [argmax_exn cmp a] is like {!argmax}, but
+    @raise Invalid_argument if [a] is empty.
+    @since NEXT_RELEASE *)
+
+val min : ('a -> 'a -> int) -> 'a t -> 'a option
+(** [min cmp a] returns [None] if [a] is empty, otherwise, returns [Some e] where [e]
+    is a minimum element in [a] with respect to [cmp].
+    @since NEXT_RELEASE *)
+
+val min_exn : ('a -> 'a -> int) -> 'a t -> 'a
+(** [min_exn cmp a] is like {!min}, but
+    @raise Invalid_argument if [a] is empty.
+    @since NEXT_RELEASE *)
+
+val argmin : ('a -> 'a -> int) -> 'a t -> int option
+(** [argmin cmp a] returns [None] if [a] is empty, otherwise, returns [Some i] where [i]
+    is the index of a minimum element in [a] with respect to [cmp].
+    @since NEXT_RELEASE *)
+
+val argmin_exn : ('a -> 'a -> int) -> 'a t -> int
+(** [argmin_exn cmp a] is like {!argmin}, but
+    @raise Invalid_argument if [a] is empty.
+    @since NEXT_RELEASE *)
+
 val lookup : cmp:'a ord -> 'a -> 'a t -> int option
 (** [lookup ~cmp key a] lookups the index of some key [key] in a sorted array [a].
     Undefined behavior if the array [a] is not sorted wrt [~cmp].

src/core/CCArrayLabels.mli

@@ -141,6 +141,47 @@ val find_idx : f:('a -> bool) -> 'a t -> (int * 'a) option
     and [f x] holds. Otherwise returns [None].
     @since 0.3.4 *)
 
+val max : cmp:('a -> 'a -> int) -> 'a t -> 'a option
+(** [max ~cmp a] returns [None] if [a] is empty, otherwise, returns [Some e] where [e]
+    is a maximum element in [a] with respect to [cmp].
+    @since NEXT_RELEASE *)
+
+val max_exn : cmp:('a -> 'a -> int) -> 'a t -> 'a
+(** [max_exn ~cmp a] is like {!max}, but
+    @raise Invalid_argument if [a] is empty.
+    @since NEXT_RELEASE *)
+
+
+val argmax : cmp:('a -> 'a -> int) -> 'a t -> int option
+(** [argmax ~cmp a] returns [None] if [a] is empty, otherwise, returns [Some i] where [i]
+    is the index of a maximum element in [a] with respect to [cmp].
+    @since NEXT_RELEASE *)
+
+val argmax_exn : cmp:('a -> 'a -> int) -> 'a t -> int
+(** [argmax_exn ~cmp a] is like {!argmax}, but
+    @raise Invalid_argument if [a] is empty.
+    @since NEXT_RELEASE *)
+
+val min : cmp:('a -> 'a -> int) -> 'a t -> 'a option
+(** [min ~cmp a] returns [None] if [a] is empty, otherwise, returns [Some e] where [e]
+    is a minimum element in [a] with respect to [cmp].
+    @since NEXT_RELEASE *)
+
+val min_exn : cmp:('a -> 'a -> int) -> 'a t -> 'a
+(** [min_exn ~cmp a] is like {!min}, but
+    @raise Invalid_argument if [a] is empty.
+    @since NEXT_RELEASE *)
+
+val argmin : cmp:('a -> 'a -> int) -> 'a t -> int option
+(** [argmin ~cmp a] returns [None] if [a] is empty, otherwise, returns [Some i] where [i]
+    is the index of a minimum element in [a] with respect to [cmp].
+    @since NEXT_RELEASE *)
+
+val argmin_exn : cmp:('a -> 'a -> int) -> 'a t -> int
+(** [argmin_exn ~cmp a] is like {!argmin}, but
+    @raise Invalid_argument if [a] is empty.
+    @since NEXT_RELEASE *)
+
 val lookup : cmp:('a ord[@keep_label]) -> key:'a -> 'a t -> int option
 (** [lookup ~cmp ~key a] lookups the index of some key [key] in a sorted array [a].
     Undefined behavior if the array [a] is not sorted wrt [cmp].

tests/core/t_array.ml

@@ -140,6 +140,22 @@ t @@ fun () -> rev [| 1; 2 |] = [| 2; 1 |];;
 t @@ fun () -> rev [||] = [||];;
 q Q.(array small_int) (fun a -> mem 1 a = Array.mem 1 a);;
 
+eq (Some 3) (max Stdlib.compare [| 1; 2; 3 |]);;
+eq (Some 4) (max Stdlib.compare [| 4; -1; 2; 3 |]);;
+eq (None) (max Stdlib.compare [||]);;
+
+eq (Some 2) (argmax Stdlib.compare [| 1; 2; 3 |]);;
+eq (Some 0) (argmax Stdlib.compare [| 4; -1; 2; 3 |]);;
+eq (None) (argmax Stdlib.compare [||]);;
+
+eq (Some 1) (min Stdlib.compare [| 1; 2; 3 |]);;
+eq (Some ~-1) (min Stdlib.compare [| 4; -1; 2; 3 |]);;
+eq (None) (min Stdlib.compare [||]);;
+
+eq (Some 0) (argmin Stdlib.compare [| 1; 2; 3 |]);;
+eq (Some 1) (argmin Stdlib.compare [| 4; -1; 2; 3 |]);;
+eq (None) (argmin Stdlib.compare [||]);;
+
 t @@ fun () ->
 filter_map
   (fun x ->