* partition.h: New file.

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+/* List implentation of a partition of consecutive integers.
+   Copyright (C) 2000 Free Software Foundation, Inc.
+   Contributed by CodeSourcery, LLC.
+
+   This file is part of GNU CC.
+
+   GNU CC 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 2, or (at your option)
+   any later version.
+
+   GNU CC 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 GNU CC; see the file COPYING.  If not, write to
+   the Free Software Foundation, 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */
+
+/* This package implements a partition of consecutive integers.  The
+   elements are partitioned into classes.  Each class is represented
+   by one of its elements, the canonical element, which is chosen
+   arbitrarily from elements in the class.  The principal operations
+   on a partition are FIND, which takes an element, determines its
+   class, and returns the canonical element for that class, and UNION,
+   which unites the two classes that contain two given elements into a
+   single class.
+
+   The list implementation used here provides constant-time finds.  By
+   storing the size of each class with the class's canonical element,
+   it is able to perform unions over all the classes in the partition
+   in O (N log N) time.  */
+
+#ifndef _PARTITION_H
+#define _PARTITION_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+
+#include <ansidecl.h>
+#include <stdio.h>
+
+struct partition_elem
+{
+  /* The canonical element that represents the class containing this
+     element.  */
+  int class_element;
+  /* The next element in this class.  Elements in each class form a
+     circular list.  */
+  struct partition_elem* next;
+  /* The number of elements in this class.  Valid only if this is the
+     canonical element for its class.  */
+  unsigned class_count;
+};
+
+typedef struct partition_def 
+{
+  /* The number of elements in this partition.  */
+  int num_elements;
+  /* The elements in the partition.  */
+  struct partition_elem elements[1];
+} *partition;
+
+extern partition partition_new          PARAMS((int));
+extern void partition_delete            PARAMS((partition));
+extern int partition_union              PARAMS((partition,
+						int,
+						int));
+extern void partition_print             PARAMS((partition,
+						FILE*));
+
+/* Returns the canonical element corresponding to the class containing
+   ELEMENT__ in PARTITION__.  */
+
+#define partition_find(partition__, element__) \
+    ((partition__)->elements[(element__)].class_element)
+
+#endif /* _PARTITION_H */