--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2009-06-29  Bruno Haible  <bruno@clisp.org>
 
+	New module 'unicase/ignorable'.
+	* lib/unicase/ignorable.c: New file.
+	* modules/unicase/ignorable: New file.
+
 	New module 'unicase/cased'.
 	* lib/unicase/caseprop.h: New file.
 	* lib/unicase/cased.c: New file.

new file mode 100644
--- /dev/null
+++ b/lib/unicase/ignorable.c
@@ -0,0 +1,46 @@
+/* Test whether a Unicode character is case-ignorable.
+   Copyright (C) 2009 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2009.
+
+   This program is free software: you can redistribute it and/or modify it
+   under the terms of the GNU Lesser General Public License as published
+   by the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include "caseprop.h"
+
+#include "unictype.h"
+#include "uniwbrk.h"
+
+bool
+uc_is_case_ignorable (ucs4_t uc)
+{
+  /* Quoting the Unicode standard:
+       Definition: A character is defined to be "case-ignorable" if it has the
+       value MidLetter {or the value MidNumLet} for the Word_Break property or
+       its General_Category is one of Nonspacing_Mark (Mn), Enclosing_Mark (Me),
+       Format (Cf), Modifier_Letter (Lm), or Modifier_Symbol (Sk).
+     The text marked in braces was added in Unicode 5.1.0, see
+     <http://www.unicode.org/versions/Unicode5.1.0/> section "Update of
+     Definition of case-ignorable".   */
+
+  int wbp = uc_wordbreak_property (uc);
+
+  return (wbp == WBP_MIDLETTER || wbp == WBP_MIDNUMLET
+	  || uc_is_general_category_withtable (uc, UC_CATEGORY_MASK_Mn
+						   | UC_CATEGORY_MASK_Me
+						   | UC_CATEGORY_MASK_Cf
+						   | UC_CATEGORY_MASK_Lm
+						   | UC_CATEGORY_MASK_Sk));
+}

new file mode 100644
--- /dev/null
+++ b/modules/unicase/ignorable
@@ -0,0 +1,27 @@
+Description:
+Test whether a Unicode character is "case-ignorable".
+
+Files:
+lib/unicase/caseprop.h
+lib/unicase/ignorable.c
+
+Depends-on:
+uniwbrk/wordbreak-property
+unictype/category-of
+unitypes
+stdbool
+
+configure.ac:
+
+Makefile.am:
+lib_SOURCES += unicase/ignorable.c
+
+Include:
+"unicase/caseprop.h"
+
+License:
+LGPL
+
+Maintainer:
+Bruno Haible
+