Initial revision

util/ego/share/lset.c

@@ -0,0 +1,208 @@
+/*  L O N G   S E T S
+ *
+ *  L S E T . C
+ */
+
+
+#include "types.h"
+#include "lset.h"
+#include "alloc.h"
+#include "debug.h"
+
+
+/* A 'long' set is represented as a linear list of 'elemholder'
+ * records. Every such record contains a pointer to an element
+ * of the set and to the next elemholder. An empty set is
+ * represented as a null pointer.
+ * An element of a long set must be of some pointer type or,
+ * in any case, must have the size of a pointer. Note that
+ * the strict typing rules are not obeyed here.
+ * This package implements the usual operations on sets.
+ * The name of every operation is preceeded by a 'L' to
+ * distinguish it from the operation on 'compact' (bitvector)
+ * sets with a similar name.
+ */
+
+
+lset Lempty_set()
+{
+	return ((lset) 0);
+}
+
+
+bool Lis_elem(x,s)
+	register Lelem_t x;
+	register lset    s;
+{
+
+	/* Search the list to see if x is an element of s */
+	while (s != (elem_p) 0) {
+		if (s->e_elem == x) {
+			return TRUE;
+		}
+		s = s->e_next;
+	}
+	return FALSE;
+}
+
+
+Ladd(x,s_p)
+	Lelem_t x;
+	lset    *s_p;
+{
+	/* add x to a set. Note that the set is given as in-out
+	 * parameter, because it may be changed.
+	 */
+
+	elem_p t;
+
+	if (!Lis_elem(x,*s_p)) {
+		t = newelem();  /* allocate a new elemholder */
+		t->e_elem = x;
+		t->e_next = *s_p;  /* insert it at the head of the list */
+		*s_p = t;
+	}
+}
+
+
+Lremove(x,s_p)
+	Lelem_t x;
+	lset    *s_p;
+{
+	/* Remove x from a set. If x was not an element of
+	 * the set, nothing happens.
+	 */
+
+	register elem_p *epp, ep;
+	lset s;
+
+	s = *s_p;
+	epp = &s;
+	while ((ep = *epp) != (elem_p) 0) {
+		if (ep->e_elem == x) {
+			*epp = ep->e_next;
+			oldelem(ep);
+			break;
+		} else {
+			epp = &ep->e_next;
+		}
+	}
+	*s_p = s;
+}
+
+
+/* The operations first, next and elem can be used to iterate
+ * over a set. For example:
+ *	for (i = Lfirst(s); i != (Lindex) 0; i = Lnext(i,s) {
+ *		x = Lelem(i);
+ *		use x
+ *	}
+ * which is like:
+ *      'for all elements x of s do'
+ *		use x
+ */
+
+
+Lindex Lfirst(s)
+	lset s;
+{
+	return ((Lindex) s);
+	/* Note that an index for long sets is just
+	 * a pointer to an elemholder.
+	 */
+}
+
+
+Lindex Lnext(i,s)
+	Lindex i;
+	lset   s;
+{
+	assert(i != (Lindex) 0);
+	return (i->e_next);
+}
+
+
+Lelem_t Lelem(i)
+	Lindex i;
+{
+	return (i->e_elem);
+}
+
+
+
+Ljoin(s1,s2_p)
+	lset s1,*s2_p;
+{
+	/* Join two sets, assign the result to the second set
+	 * and delete the first set (i.e. the value of the
+	 * first set becomes undefined).
+	 */
+
+	 register elem_p *epp, ep;
+	 lset s2;
+
+	 /* First all elements of s1 that are also an element of s2
+	  * are removed from the s1 list. The two resulting lists
+	  * (for s1 and s2) are linked (s1 first).
+	  * Note the usage of epp, which points to a pointer that
+	  * points to the next elemholder record of the list.
+	  */
+
+	s2 = *s2_p;
+	epp = &s1;
+	while ((ep = *epp) != (elem_p) 0) {
+		if (Lis_elem(ep->e_elem,s2)) {
+			/* remove an element */
+			*epp = ep->e_next;
+			oldelem(ep);
+		} else {
+			epp = &ep->e_next;
+		}
+	}
+	*epp = s2; /* last record of s1 (or s1 itself) now points
+		    * to first record of s2.
+		    */
+	*s2_p = s1;
+}
+
+
+Ldeleteset(s)
+	lset s;
+{
+	register elem_p ep, next;
+
+	for (ep = s; ep != (elem_p) 0; ep = next) {
+		next = ep->e_next;
+		oldelem(ep);
+	}
+}
+
+
+bool Lis_subset(s1,s2)
+	lset s1,s2;
+{
+	/* See if s1 is a subset of s2 */
+
+	register Lindex i;
+
+	for (i = Lfirst(s1); i != (Lindex) 0; i = Lnext(i,s1)) {
+		if (!Lis_elem(Lelem(i),s2)) return FALSE;
+	}
+	return TRUE;
+}
+
+
+short Lnrelems(s)
+	lset s;
+{
+	/* Compute the number of elements of a set */
+
+	register elem_p ep;
+	register short  cnt;
+
+	cnt = 0;
+	for (ep = s; ep != (elem_p) 0; ep = ep->e_next) {
+		cnt++;
+	}
+	return cnt;
+}