add CCstring.equal_caseless (close #112)

src/core/CCString.cppo.ml

@@ -391,17 +391,6 @@ end
 let split_on_char c s: _ list =
   Split.list_cpy ~by:(String.make 1 c) s
 
-(*$= & ~printer:Q.Print.(list string)
-  ["a"; "few"; "words"; "from"; "our"; "sponsors"] \
-    (split_on_char ' ' "a few words from our sponsors")
-*)
-
-(*$Q
-  Q.(printable_string) (fun s -> \
-    let s = split_on_char ' ' s |> String.concat " " in \
-    s = split_on_char ' ' s |> String.concat " ")
-*)
-
 let split = Split.list_cpy
 
 let compare_versions a b =
@@ -721,7 +710,16 @@ let lowercase_ascii = map CCChar.lowercase_ascii
 
     #endif
 
-
+let equal_caseless s1 s2: bool =
+  let char_lower c =
+    if c >= 'A' && c <= 'Z'
+    then Char.unsafe_chr (Char. code c + 32)
+    else c
+  in
+  String.length s1 = String.length s2 &&
+  for_all2
+    (fun c1 c2 -> Char.equal (char_lower c1) (char_lower c2))
+    s1 s2
 
 let pp buf s =
   Buffer.add_char buf '"';

src/core/CCString.mli

@@ -399,6 +399,22 @@ val uppercase_ascii : string -> string
 val lowercase_ascii : string -> string
 (** See {!String}. @since 0.18 *)
 
+val equal_caseless : string -> string -> bool
+(** Comparison without respect to {b ascii} lowercase.
+    @since NEXT_RELEASE *)
+
+(*$T
+  equal_caseless "foo" "FoO"
+  equal_caseless "helLo" "HEllO"
+*)
+
+(*$Q
+  Q.(pair printable_string printable_string) (fun (s1,s2) -> \
+    equal_caseless s1 s2 = equal (lowercase_ascii s1)(lowercase_ascii s2))
+  Q.(printable_string) (fun s -> equal_caseless s s)
+  Q.(printable_string) (fun s -> equal_caseless (uppercase_ascii s) s)
+*)
+
 (** {2 Finding}
 
     A relatively efficient algorithm for finding sub-strings
@@ -499,6 +515,17 @@ val split_on_char : char -> string -> string list
 (** Split the string along the given char
     @since NEXT_RELEASE *)
 
+(*$= & ~printer:Q.Print.(list string)
+  ["a"; "few"; "words"; "from"; "our"; "sponsors"] \
+    (split_on_char ' ' "a few words from our sponsors")
+*)
+
+(*$Q
+  Q.(printable_string) (fun s -> \
+    let s = split_on_char ' ' s |> String.concat " " in \
+    s = (split_on_char ' ' s |> String.concat " "))
+*)
+
 val split : by:string -> string -> string list
 (** Alias to {!Split.list_cpy}
     @since NEXT_RELEASE *)