CCFormat: add append, append_l, infix ++ for sequencing

src/core/CCFormat.ml

@@ -107,6 +107,24 @@ let triple ?(sep=return ",@ ") ppa ppb ppc fmt (a, b, c) =
 let quad ?(sep=return ",@ ") ppa ppb ppc ppd fmt (a, b, c, d) =
   Format.fprintf fmt "%a%a%a%a%a%a%a" ppa a sep () ppb b sep () ppc c sep () ppd d
 
+let append ppa ppb fmt () =
+  ppa fmt ();
+  ppb fmt ()
+
+(*$= append & ~printer:(fun s -> CCFormat.sprintf "%S" s)
+  "foobar" (to_string_test (append (return "foo") (return "bar")))
+  "bar" (to_string_test (append (return "") (return "bar")))
+  "foo" (to_string_test (append (return "foo") (return "")))
+*)
+
+let append_l = List.fold_left append (return "")
+
+(*$= append_l & ~printer:(fun s -> CCFormat.sprintf "%S" s)
+  "" (to_string_test @@ append_l [])
+  "foobarbaz" (to_string_test @@ append_l (List.map return ["foo"; "bar"; "baz"]))
+  "3141" (to_string_test @@ append_l (List.map (const int) [3; 14; 1]))
+*)
+
 let within a b p out x =
   string out a;
   p out x;
@@ -444,3 +462,9 @@ end
   "[(Ok \"a b c\");(Error \"nope\")]" \
     (to_string Dump.(list (result string)) [Ok "a b c"; Error "nope"])
 *)
+
+module Infix = struct
+  let (++) = append
+end
+
+include Infix

src/core/CCFormat.mli

@@ -95,6 +95,12 @@ val triple : ?sep:unit printer -> 'a printer -> 'b printer -> 'c printer -> ('a
 val quad : ?sep:unit printer -> 'a printer -> 'b printer ->
   'c printer -> 'd printer -> ('a * 'b * 'c * 'd) printer
 
+val append : unit printer -> unit printer -> unit printer
+(** [append ppa ppb] first prints [ppa ()], then prints [ppb ()]. *)
+
+val append_l : unit printer list -> unit printer
+(** [append_l pps] runs the printers in [pps] sequentially. *)
+
 val within : string -> string -> 'a printer -> 'a printer
 (** [within a b p] wraps [p] inside the strings [a] and [b]. Convenient,
     for instances, for brackets, parenthesis, quotes, etc.
@@ -349,3 +355,10 @@ module Dump : sig
   val to_string : 'a t -> 'a -> string
   (** Alias to {!CCFormat.to_string}. *)
 end
+
+module Infix : sig
+  val (++) : unit printer -> unit printer -> unit printer
+  (** Alias to {!append}. *)
+end
+
+include module type of Infix