--- a/ChangeLog	Fri Dec 07 06:26:08 2018 +0100
+++ b/ChangeLog	Tue Dec 04 00:41:24 2018 +0100
@@ -1,3 +1,12 @@
+2018-12-03  Bruno Haible  <bruno@clisp.org>
+
+	set: New module.
+	* lib/gl_set.h: New file.
+	* lib/gl_set.c: New file.
+	* lib/gl_oset.h (gl_setelement_dispose_fn): Avoid conflict with
+	gl_set.h.
+	* modules/set: New file.
+
 2018-12-07  Akim Demaille  <akim@lrde.epita.fr>
 
 	bison: don't force the Yacc mode

--- a/lib/gl_oset.h	Fri Dec 07 06:26:08 2018 +0100
+++ b/lib/gl_oset.h	Tue Dec 04 00:41:24 2018 +0100
@@ -77,9 +77,12 @@
    NULL denotes pointer comparison.  */
 typedef int (*gl_setelement_compar_fn) (const void *elt1, const void *elt2);
 
+#ifndef _GL_SETELEMENT_DISPOSE_FN_DEFINED
 /* Type of function used to dispose an element once it's removed from a set.
    NULL denotes a no-op.  */
 typedef void (*gl_setelement_dispose_fn) (const void *elt);
+# define _GL_SETELEMENT_DISPOSE_FN_DEFINED 1
+#endif
 
 /* Type of function used to compare an element with a threshold.
    Return true if the element is greater or equal than the threshold.  */
@@ -144,7 +147,7 @@
    (But this call does not free the elements of the set.)  */
 extern void gl_oset_free (gl_oset_t set);
 
-#endif /* End of inline and gl_xlist.h-defined functions.  */
+#endif /* End of inline and gl_xoset.h-defined functions.  */
 
 /* --------------------- gl_oset_iterator_t Data Type --------------------- */
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/gl_set.c	Tue Dec 04 00:41:24 2018 +0100
@@ -0,0 +1,3 @@
+#include <config.h>
+#define GL_SET_INLINE _GL_EXTERN_INLINE
+#include "gl_set.h"

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/gl_set.h	Tue Dec 04 00:41:24 2018 +0100
@@ -0,0 +1,280 @@
+/* Abstract set data type.
+   Copyright (C) 2006-2007, 2009-2018 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2018.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#ifndef _GL_SET_H
+#define _GL_SET_H
+
+#include <stdbool.h>
+#include <stddef.h>
+
+#ifndef _GL_INLINE_HEADER_BEGIN
+ #error "Please include config.h first."
+#endif
+_GL_INLINE_HEADER_BEGIN
+#ifndef GL_SET_INLINE
+# define GL_SET_INLINE _GL_INLINE
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/* gl_set is an abstract set data type.  It can contain any number of objects
+   ('void *' or 'const void *' pointers); the order does not matter.
+   Duplicates (in the sense of the comparator) are forbidden.
+
+   There are several implementations of this set datatype, optimized for
+   different operations or for memory.  You can start using the simplest set
+   implementation, GL_ARRAY_SET, and switch to a different implementation
+   later, when you realize which operations are performed the most frequently.
+   The API of the different implementations is exactly the same; when switching
+   to a different implementation, you only have to change the gl_set_create
+   call.
+
+   The implementations are:
+     GL_ARRAY_SET         a growable array
+     GL_LINKEDHASH_SET    a hash table with a linked list
+     GL_HASH_SET          a hash table
+
+   The memory consumption is asymptotically the same: O(1) for every object
+   in the set.  When looking more closely at the average memory consumed
+   for an object, GL_ARRAY_SET is the most compact representation, then comes
+   GL_HASH_SET, and GL_LINKEDHASH_SET needs the most memory.
+
+   The guaranteed average performance of the operations is, for a set of
+   n elements:
+
+   Operation                  ARRAY   LINKEDHASH
+                                      HASH
+
+   gl_set_size                 O(1)   O(1)
+   gl_set_add                  O(n)   O(1)
+   gl_set_remove               O(n)   O(1)
+   gl_set_search               O(n)   O(1)
+   gl_set_iterator             O(1)   O(1)
+   gl_set_iterator_next        O(1)   O(1)
+ */
+
+/* --------------------------- gl_set_t Data Type --------------------------- */
+
+/* Type of function used to compare two elements.
+   NULL denotes pointer comparison.  */
+typedef bool (*gl_setelement_equals_fn) (const void *elt1, const void *elt2);
+
+/* Type of function used to compute a hash code.
+   NULL denotes a function that depends only on the pointer itself.  */
+typedef size_t (*gl_setelement_hashcode_fn) (const void *elt);
+
+#ifndef _GL_SETELEMENT_DISPOSE_FN_DEFINED
+/* Type of function used to dispose an element once it's removed from a set.
+   NULL denotes a no-op.  */
+typedef void (*gl_setelement_dispose_fn) (const void *elt);
+# define _GL_SETELEMENT_DISPOSE_FN_DEFINED 1
+#endif
+
+struct gl_set_impl;
+/* Type representing an entire set.  */
+typedef struct gl_set_impl * gl_set_t;
+
+struct gl_set_implementation;
+/* Type representing a set datatype implementation.  */
+typedef const struct gl_set_implementation * gl_set_implementation_t;
+
+#if 0 /* Unless otherwise specified, these are defined inline below.  */
+
+/* Create an empty set.
+   IMPLEMENTATION is one of GL_ARRAY_SET, GL_LINKEDHASH_SET, GL_HASH_SET.
+   EQUALS_FN is an element comparison function or NULL.
+   HASHCODE_FN is an element hash code function or NULL.
+   DISPOSE_FN is an element disposal function or NULL.  */
+/* declared in gl_xset.h */
+extern gl_set_t gl_set_create_empty (gl_set_implementation_t implementation,
+                                     gl_setelement_equals_fn equals_fn,
+                                     gl_setelement_hashcode_fn hashcode_fn,
+                                     gl_setelement_dispose_fn dispose_fn);
+/* Likewise.  Return NULL upon out-of-memory.  */
+extern gl_set_t gl_set_nx_create_empty (gl_set_implementation_t implementation,
+                                        gl_setelement_equals_fn equals_fn,
+                                        gl_setelement_hashcode_fn hashcode_fn,
+                                        gl_setelement_dispose_fn dispose_fn);
+
+/* Return the current number of elements in a set.  */
+extern size_t gl_set_size (gl_set_t set);
+
+/* Search whether an element is already in the set.
+   Return true if found, or false if not present in the set.  */
+extern bool gl_set_search (gl_set_t set, const void *elt);
+
+/* Add an element to a set.
+   Return true if it was not already in the set and added, false otherwise.  */
+/* declared in gl_xset.h */
+extern bool gl_set_add (gl_set_t set, const void *elt);
+/* Likewise.  Return -1 upon out-of-memory.  */
+extern int gl_set_nx_add (gl_set_t set, const void *elt)
+#if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
+  __attribute__ ((__warn_unused_result__))
+#endif
+  ;
+
+/* Remove an element from a set.
+   Return true if it was found and removed.  */
+extern bool gl_set_remove (gl_set_t set, const void *elt);
+
+/* Free an entire set.
+   (But this call does not free the elements of the set.)  */
+extern void gl_set_free (gl_set_t set);
+
+#endif /* End of inline and gl_xset.h-defined functions.  */
+
+/* ---------------------- gl_set_iterator_t Data Type ---------------------- */
+
+/* Functions for iterating through a set.
+   Note: Iterating through a set of type GL_HASH_SET returns the elements in an
+   unpredictable order.  If you need a predictable order, use GL_LINKEDHASH_SET
+   instead of GL_HASH_SET.  */
+
+/* Type of an iterator that traverses a set.
+   This is a fixed-size struct, so that creation of an iterator doesn't need
+   memory allocation on the heap.  */
+typedef struct
+{
+  /* For fast dispatch of gl_set_iterator_next.  */
+  const struct gl_set_implementation *vtable;
+  /* For detecting whether the last returned element was removed.  */
+  gl_set_t set;
+  size_t count;
+  /* Other, implementation-private fields.  */
+  void *p; void *q;
+  size_t i; size_t j;
+} gl_set_iterator_t;
+
+#if 0 /* These are defined inline below.  */
+
+/* Create an iterator traversing a set.
+   The set's contents must not be modified while the iterator is in use,
+   except for removing the last returned element.  */
+extern gl_set_iterator_t gl_set_iterator (gl_set_t set);
+
+/* If there is a next element, store the next element in *ELTP, advance the
+   iterator and return true.  Otherwise, return false.  */
+extern bool gl_set_iterator_next (gl_set_iterator_t *iterator,
+                                  const void **eltp);
+
+/* Free an iterator.  */
+extern void gl_set_iterator_free (gl_set_iterator_t *iterator);
+
+#endif /* End of inline functions.  */
+
+/* ------------------------ Implementation Details ------------------------ */
+
+struct gl_set_implementation
+{
+  /* gl_set_t functions.  */
+  gl_set_t (*nx_create_empty) (gl_set_implementation_t implementation,
+                               gl_setelement_equals_fn equals_fn,
+                               gl_setelement_hashcode_fn hashcode_fn,
+                               gl_setelement_dispose_fn dispose_fn);
+  size_t (*size) (gl_set_t set);
+  bool (*search) (gl_set_t set, const void *elt);
+  int (*nx_add) (gl_set_t set, const void *elt);
+  bool (*remove_elt) (gl_set_t set, const void *elt);
+  void (*set_free) (gl_set_t set);
+  /* gl_set_iterator_t functions.  */
+  gl_set_iterator_t (*iterator) (gl_set_t set);
+  bool (*iterator_next) (gl_set_iterator_t *iterator, const void **eltp);
+  void (*iterator_free) (gl_set_iterator_t *iterator);
+};
+
+struct gl_set_impl_base
+{
+  const struct gl_set_implementation *vtable;
+  gl_setelement_equals_fn equals_fn;
+  gl_setelement_dispose_fn dispose_fn;
+};
+
+/* Define all functions of this file as accesses to the
+   struct gl_set_implementation.  */
+
+GL_SET_INLINE gl_set_t
+gl_set_nx_create_empty (gl_set_implementation_t implementation,
+                        gl_setelement_equals_fn equals_fn,
+                        gl_setelement_hashcode_fn hashcode_fn,
+                        gl_setelement_dispose_fn dispose_fn)
+{
+  return implementation->nx_create_empty (implementation, equals_fn,
+                                          hashcode_fn, dispose_fn);
+}
+
+GL_SET_INLINE size_t
+gl_set_size (gl_set_t set)
+{
+  return ((const struct gl_set_impl_base *) set)->vtable->size (set);
+}
+
+GL_SET_INLINE bool
+gl_set_search (gl_set_t set, const void *elt)
+{
+  return ((const struct gl_set_impl_base *) set)->vtable->search (set, elt);
+}
+
+GL_SET_INLINE int
+#if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
+  __attribute__ ((__warn_unused_result__))
+#endif
+gl_set_nx_add (gl_set_t set, const void *elt)
+{
+  return ((const struct gl_set_impl_base *) set)->vtable->nx_add (set, elt);
+}
+
+GL_SET_INLINE bool
+gl_set_remove (gl_set_t set, const void *elt)
+{
+  return ((const struct gl_set_impl_base *) set)->vtable->remove_elt (set, elt);
+}
+
+GL_SET_INLINE void
+gl_set_free (gl_set_t set)
+{
+  ((const struct gl_set_impl_base *) set)->vtable->set_free (set);
+}
+
+GL_SET_INLINE gl_set_iterator_t
+gl_set_iterator (gl_set_t set)
+{
+  return ((const struct gl_set_impl_base *) set)->vtable->iterator (set);
+}
+
+GL_SET_INLINE bool
+gl_set_iterator_next (gl_set_iterator_t *iterator, const void **eltp)
+{
+  return iterator->vtable->iterator_next (iterator, eltp);
+}
+
+GL_SET_INLINE void
+gl_set_iterator_free (gl_set_iterator_t *iterator)
+{
+  iterator->vtable->iterator_free (iterator);
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+_GL_INLINE_HEADER_END
+
+#endif /* _GL_SET_H */

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/modules/set	Tue Dec 04 00:41:24 2018 +0100
@@ -0,0 +1,24 @@
+Description:
+Abstract set data type.
+
+Files:
+lib/gl_set.h
+lib/gl_set.c
+
+Depends-on:
+extern-inline
+stdbool
+
+configure.ac:
+
+Makefile.am:
+lib_SOURCES += gl_set.h gl_set.c
+
+Include:
+"gl_set.h"
+
+License:
+GPL
+
+Maintainer:
+all