--- a/ChangeLog	Tue Dec 04 00:41:24 2018 +0100
+++ b/ChangeLog	Tue Dec 04 00:43:22 2018 +0100
@@ -1,5 +1,10 @@
 2018-12-03  Bruno Haible  <bruno@clisp.org>
 
+	array-set: New module.
+	* lib/gl_array_set.h: New file.
+	* lib/gl_array_set.c: New file.
+	* modules/array-set: New file.
+
 	set: New module.
 	* lib/gl_set.h: New file.
 	* lib/gl_set.c: New file.

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/gl_array_set.c	Tue Dec 04 00:43:22 2018 +0100
@@ -0,0 +1,256 @@
+/* Set data type implemented by an array.
+   Copyright (C) 2006-2018 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/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include "gl_array_set.h"
+
+#include <stdlib.h>
+
+/* Checked size_t computations.  */
+#include "xsize.h"
+
+#ifndef uintptr_t
+# define uintptr_t unsigned long
+#endif
+
+/* --------------------------- gl_set_t Data Type --------------------------- */
+
+/* Concrete gl_set_impl type, valid for this file only.  */
+struct gl_set_impl
+{
+  struct gl_set_impl_base base;
+  /* An array of ALLOCATED elements, of which the first COUNT are used.
+     0 <= COUNT <= ALLOCATED.  */
+  const void **elements;
+  size_t count;
+  size_t allocated;
+};
+
+static gl_set_t
+gl_array_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)
+{
+  struct gl_set_impl *set =
+    (struct gl_set_impl *) malloc (sizeof (struct gl_set_impl));
+
+  if (set == NULL)
+    return NULL;
+
+  set->base.vtable = implementation;
+  set->base.equals_fn = equals_fn;
+  set->base.dispose_fn = dispose_fn;
+  set->elements = NULL;
+  set->count = 0;
+  set->allocated = 0;
+
+  return set;
+}
+
+static size_t
+gl_array_size (gl_set_t set)
+{
+  return set->count;
+}
+
+static bool
+gl_array_search (gl_set_t set, const void *elt)
+{
+  size_t count = set->count;
+
+  if (count > 0)
+    {
+      gl_setelement_equals_fn equals = set->base.equals_fn;
+      const void **elements = set->elements;
+      size_t i;
+
+      for (i = 0; i < count; i++)
+        if (equals != NULL ? equals (elements[i], elt) : elements[i] == elt)
+          return true;
+    }
+  return false;
+}
+
+/* Ensure that set->allocated > set->count.
+   Return 0 upon success, -1 upon out-of-memory.  */
+static int
+grow (gl_set_t set)
+{
+  size_t new_allocated;
+  size_t memory_size;
+  const void **memory;
+
+  new_allocated = xtimes (set->allocated, 2);
+  new_allocated = xsum (new_allocated, 1);
+  memory_size = xtimes (new_allocated, sizeof (const void *));
+  if (size_overflow_p (memory_size))
+    /* Overflow, would lead to out of memory.  */
+    return -1;
+  memory = (const void **) realloc (set->elements, memory_size);
+  if (memory == NULL)
+    /* Out of memory.  */
+    return -1;
+  set->elements = memory;
+  set->allocated = new_allocated;
+  return 0;
+}
+
+static int
+gl_array_nx_add (gl_set_t set, const void *elt)
+{
+  if (gl_array_search (set, elt))
+    return 0;
+  else
+    {
+      size_t count = set->count;
+
+      if (count == set->allocated)
+        if (grow (set) < 0)
+          return -1;
+      set->elements[count] = elt;
+      set->count = count + 1;
+      return 1;
+    }
+}
+
+/* Remove the element at the given position,
+   0 <= position < gl_set_size (set).  */
+static void
+gl_array_remove_at (gl_set_t set, size_t position)
+{
+  size_t count = set->count;
+  const void **elements = set->elements;
+  size_t i;
+
+  if (set->base.dispose_fn != NULL)
+    set->base.dispose_fn (elements[position]);
+  for (i = position + 1; i < count; i++)
+    elements[i - 1] = elements[i];
+  set->count = count - 1;
+}
+
+static bool
+gl_array_remove (gl_set_t set, const void *elt)
+{
+  size_t count = set->count;
+
+  if (count > 0)
+    {
+      gl_setelement_equals_fn equals = set->base.equals_fn;
+      const void **elements = set->elements;
+      size_t i;
+
+      for (i = 0; i < count; i++)
+        if (equals != NULL ? equals (elements[i], elt) : elements[i] == elt)
+          {
+            gl_array_remove_at (set, i);
+            return true;
+          }
+    }
+  return false;
+}
+
+static void
+gl_array_free (gl_set_t set)
+{
+  if (set->elements != NULL)
+    {
+      if (set->base.dispose_fn != NULL)
+        {
+          size_t count = set->count;
+
+          if (count > 0)
+            {
+              gl_setelement_dispose_fn dispose = set->base.dispose_fn;
+              const void **elements = set->elements;
+
+              do
+                dispose (*elements++);
+              while (--count > 0);
+            }
+        }
+      free (set->elements);
+    }
+  free (set);
+}
+
+/* ---------------------- gl_set_iterator_t Data Type ---------------------- */
+
+static gl_set_iterator_t
+gl_array_iterator (gl_set_t set)
+{
+  gl_set_iterator_t result;
+
+  result.vtable = set->base.vtable;
+  result.set = set;
+  result.count = set->count;
+  result.p = set->elements + 0;
+  result.q = set->elements + set->count;
+#if defined GCC_LINT || defined lint
+  result.i = 0;
+  result.j = 0;
+#endif
+
+  return result;
+}
+
+static bool
+gl_array_iterator_next (gl_set_iterator_t *iterator, const void **eltp)
+{
+  gl_set_t set = iterator->set;
+  if (iterator->count != set->count)
+    {
+      if (iterator->count != set->count + 1)
+        /* Concurrent modifications were done on the set.  */
+        abort ();
+      /* The last returned element was removed.  */
+      iterator->count--;
+      iterator->p = (const void **) iterator->p - 1;
+      iterator->q = (const void **) iterator->q - 1;
+    }
+  if (iterator->p < iterator->q)
+    {
+      const void **p = (const void **) iterator->p;
+      *eltp = *p;
+      iterator->p = p + 1;
+      return true;
+    }
+  else
+    return false;
+}
+
+static void
+gl_array_iterator_free (gl_set_iterator_t *iterator)
+{
+}
+
+
+const struct gl_set_implementation gl_array_set_implementation =
+  {
+    gl_array_nx_create_empty,
+    gl_array_size,
+    gl_array_search,
+    gl_array_nx_add,
+    gl_array_remove,
+    gl_array_free,
+    gl_array_iterator,
+    gl_array_iterator_next,
+    gl_array_iterator_free
+  };

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/gl_array_set.h	Tue Dec 04 00:43:22 2018 +0100
@@ -0,0 +1,34 @@
+/* Set data type implemented by an array.
+   Copyright (C) 2006, 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_ARRAY_SET_H
+#define _GL_ARRAY_SET_H
+
+#include "gl_set.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern const struct gl_set_implementation gl_array_set_implementation;
+#define GL_ARRAY_SET &gl_array_set_implementation
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _GL_ARRAY_SET_H */

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/modules/array-set	Tue Dec 04 00:43:22 2018 +0100
@@ -0,0 +1,24 @@
+Description:
+Set data type implemented by an array.
+
+Files:
+lib/gl_array_set.h
+lib/gl_array_set.c
+
+Depends-on:
+set
+xsize
+
+configure.ac:
+
+Makefile.am:
+lib_SOURCES += gl_array_set.h gl_array_set.c
+
+Include:
+"gl_array_set.h"
+
+License:
+GPL
+
+Maintainer:
+all