Restrict POSIX character classes to 7-bit ASCII, i.e. POSIX locale (#4)

Including the example from the original issue description, as well as
many extra test cases for the "cntrl" POSIX class, as that one was
most tricky to express.

Author: vog

README.md

@@ -63,7 +63,7 @@ function%mikmatch {|/ "hello" / u|} -> "matched" (* matches "hello world" *)
 
 Available in patterns:
 
-**POSIX character classes:** `lower`, `upper`, `alpha`, `digit`, `alnum`, `punct`, `graph`, `print`, `blank`, `space`, `cntrl`, `xdigit`
+**POSIX character classes:** `lower`, `upper`, `alpha`, `digit`, `alnum`, `punct`, `graph`, `print`, `blank`, `space`, `cntrl`, `xdigit` (7-bit ASCII, i.e. POSIX locale)
 
 **Control sequences:**
 - `bos` - beginning of string (`^`)

lib/mik_lexer.mll

@@ -6,19 +6,19 @@ let new_line lexbuf =
   Lexing.new_line lexbuf
 
 let predefined_classes = [
-  ("lower", {|[[:lower:]]|});
-  ("upper", {|[[:upper:]]|});
-  ("alpha", {|[[:alpha:]]|});
-  ("digit", {|[[:digit:]]|});
-  ("alnum", {|[[:alnum:]]|});
-  ("punct", {|[[:punct:]]|});
-  ("graph", {|[[:graph:]]|});
-  ("print", {|[[:print:]]|});
-  ("blank", {|[[:blank:]]|});
-  ("cntrl", {|[[:cntrl:]]|});
-  ("xdigit", {|[[:xdigit:]]|});
-  ("space", {|[[:space:]]|});
-  (* ("word", {|[[:word:]]|}); *)
+  ("lower", {|[a-z]|});
+  ("upper", {|[A-Z]|});
+  ("alpha", {|[A-Za-z]|});
+  ("digit", {|[0-9]|});
+  ("alnum", {|[0-9A-Za-z]|});
+  ("punct", {|[!-/:-@[-`{-~]|});
+  ("graph", {|[!-~]|});
+  ("print", {|[ -~]|});
+  ("blank", {|[\t ]|});
+  ("cntrl", "[\x00-\x1f\x7f]");
+  ("xdigit", {|[0-9A-Fa-f]]|});
+  ("space", {|[\t-\r ]|});
+  (* ("word", {|[0-9A-Za-z_]|}); *)
   ("eos", {|$|});
   ("eol", {|$|[\n]|});
   ("bnd", {|\b|});

tests/test_ppx_mikmatch.ml

@@ -8,6 +8,27 @@ let test_basic_matching _ =
   assert_equal "matched hello" (match_hello "hello");
   assert_equal "no match" (match_hello "world");
 
+  let match_lower = function%mikmatch {| lower |} -> "lower" | _ -> "not lower" in
+  assert_equal "lower" (match_lower "a");
+  assert_equal "not lower" (match_lower "A");
+  assert_equal "not lower" (match_lower "\xb5");
+
+  let match_cntrl = function%mikmatch {| cntrl |} -> "control character" | _ -> "not a control character" in
+  assert_equal "control character" (match_cntrl "\x00");
+  assert_equal "control character" (match_cntrl "\x01");
+  assert_equal "control character" (match_cntrl "\t");
+  assert_equal "control character" (match_cntrl "\n");
+  assert_equal "control character" (match_cntrl "\x1f");
+  assert_equal "control character" (match_cntrl "\x7f");
+  assert_equal "not a control character" (match_cntrl "");
+  assert_equal "not a control character" (match_cntrl "\x00\x00");
+  assert_equal "not a control character" (match_cntrl " ");
+  assert_equal "not a control character" (match_cntrl "~");
+  assert_equal "not a control character" (match_cntrl "\x80");
+  assert_equal "not a control character" (match_cntrl "\x81");
+  assert_equal "not a control character" (match_cntrl "\x9f");
+  assert_equal "not a control character" (match_cntrl "\xff");
+
   let match_digit = function%mikmatch {| digit |} -> "single digit" | _ -> "not a digit" in
   assert_equal "single digit" (match_digit "5");
   assert_equal "not a digit" (match_digit "a");
@@ -422,7 +443,7 @@ let test_mixed_matching _ =
 
   assert_equal "got a" (no_default_case "a");
   assert_equal "got b" (no_default_case "b");
-  assert_raises (Failure "File tests/test_ppx_mikmatch.ml, lines 417-419, characters 24-33: String did not match any mikmatch cases.")
+  assert_raises (Failure "File tests/test_ppx_mikmatch.ml, lines 438-440, characters 24-33: String did not match any mikmatch cases.")
     (fun () -> no_default_case "c")
 
 type mode =