add CCString.{l,r}trim (close #121)

src/core/CCString.cppo.ml

@@ -652,6 +652,21 @@ let exists p s =
   try iter (fun c -> if p c then raise MyExit) s; false
   with MyExit -> true
 
+(* notion of whitespace for trim *)
+let is_space_ = function
+  | ' ' | '\012' | '\n' | '\r' | '\t' -> true
+  | _ -> false
+
+let ltrim s =
+  let i = ref 0 in
+  while !i < length s && is_space_ (unsafe_get s !i) do incr i done;
+  if !i > 0 then sub s !i (length s - !i) else s
+
+let rtrim s =
+  let i = ref (length s-1) in
+  while !i >= 0 && is_space_ (unsafe_get s !i) do decr i done;
+  if !i < length s-1 then sub s 0 (!i+1) else s
+
 let map2 f s1 s2 =
   if length s1 <> length s2 then invalid_arg "CCString.map2";
   init (String.length s1) (fun i -> f s1.[i] s2.[i])

src/core/CCString.mli

@@ -351,6 +351,32 @@ val exists : (char -> bool) -> string -> bool
 
 include S with type t := string
 
+val ltrim : t -> t
+(** trim space on the left (see {!String.trim} for more details)
+    @since NEXT_RELEASE *)
+
+val rtrim : t -> t
+(** trim space on the right (see {!String.trim} for more details)
+    @since NEXT_RELEASE *)
+
+(*$= & ~printer:id
+  "abc " (ltrim " abc ")
+  " abc" (rtrim " abc ")
+*)
+
+(*$Q
+  Q.(printable_string) (fun s -> \
+    String.trim s = (s |> ltrim |> rtrim))
+  Q.(printable_string) (fun s -> ltrim s = ltrim (ltrim s))
+  Q.(printable_string) (fun s -> rtrim s = rtrim (rtrim s))
+  Q.(printable_string) (fun s -> \
+    let s' = ltrim s in \
+    if s'="" then Q.assume_fail() else s'.[0] <> ' ')
+  Q.(printable_string) (fun s -> \
+    let s' = rtrim s in \
+    if s'="" then Q.assume_fail() else s'.[String.length s'-1] <> ' ')
+  *)
+
 (** {2 Operations on 2 strings} *)
 
 val map2 : (char -> char -> char) -> string -> string -> string