From 5eedc859046c58e8649bb32b040d192e28daac51 Mon Sep 17 00:00:00 2001
From: erg <devnull@localhost>
Date: Sat, 20 Dec 2008 21:20:31 +0000
Subject: [PATCH] Fix cgraph to have the same semantics as libgraph concerning
 strict graphs. That is, strict means no multiedges; it does not preclude
 loops.

Added a bit to allow a graph to also disallow loops, though this is
unsed at present.
---
 lib/cgraph/cgraph.h |  4 +++-
 lib/cgraph/edge.c   | 22 +++++++++++-----------
 lib/cgraph/graph.c  |  5 +++++
 3 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/lib/cgraph/cgraph.h b/lib/cgraph/cgraph.h
index 3249dd32c..d91f56261 100644
--- a/lib/cgraph/cgraph.h
+++ b/lib/cgraph/cgraph.h
@@ -139,7 +139,8 @@ struct Agedgepair_s {
 
 struct Agdesc_s {		/* graph descriptor */
     unsigned directed:1;	/* if edges are asymmetric */
-    unsigned strict:1;		/* if and self, multi-edges forbidden */
+    unsigned strict:1;		/* if multi-edges forbidden */
+    unsigned no_loop:1;		/* if no loops */
     unsigned maingraph:1;	/* if this is the top level graph */
     unsigned flatlock:1;	/* if sets are flattened into lists in cdt */
     unsigned no_write:1;	/* if a temporary subgraph */
@@ -266,6 +267,7 @@ extern int agwrite(Agraph_t * g, void *chan);
 extern int agisdirected(Agraph_t * g);
 extern int agisundirected(Agraph_t * g);
 extern int agisstrict(Agraph_t * g);
+extern int agissimple(Agraph_t * g);
 
 /* nodes */
 extern Agnode_t *agnode(Agraph_t * g, char *name, int createflag);
diff --git a/lib/cgraph/edge.c b/lib/cgraph/edge.c
index ece00f71b..0b716198d 100644
--- a/lib/cgraph/edge.c
+++ b/lib/cgraph/edge.c
@@ -113,15 +113,19 @@ static Agedge_t *agfindedge_by_key(Agraph_t * g, Agnode_t * t, Agnode_t * h,
     sn = agsubrep(g, h);
     if (!sn) e = 0;
     else {
+#if 0
 	if (t != h) {
+#endif
 	    dtrestore(g->e_id, sn->in_id);
 	    e = (Agedge_t *) dtsearch(g->e_id, &template);
 	    sn->in_id = dtextract(g->e_id);
+#if 0
 	} else {			/* self edge */
 	    dtrestore(g->e_id, sn->out_id);
 	    e = (Agedge_t *) dtsearch(g->e_id, &template);
 	    sn->out_id = dtextract(g->e_id);
 	}
+#endif
     }
     return e;
 }
@@ -175,11 +179,9 @@ static void installedge(Agraph_t * g, Agedge_t * e)
 	sn = agsubrep(g, t);
 	ins(g->e_seq, &sn->out_seq, out);
 	ins(g->e_id, &sn->out_id, out);
-	if (t != h) {
-	    sn = agsubrep(g, h);
-	    ins(g->e_seq, &sn->in_seq, in);
-	    ins(g->e_id, &sn->in_id, in);
-	}
+	sn = agsubrep(g, h);
+	ins(g->e_seq, &sn->in_seq, in);
+	ins(g->e_id, &sn->in_id, in);
 	g = agparent(g);
     }
 }
@@ -224,7 +226,7 @@ static int ok_to_make_edge(Agraph_t * g, Agnode_t * t, Agnode_t * h)
 
     /* protect against self, multi-edges in strict graphs */
     if (agisstrict(g)) {
-	if (t == h)
+	if (g->desc.no_loop && (t == h)) /* simple graphs */
 	    return FALSE;
 	key = Tag;
 	key.objtype = 0;	/* wild card */
@@ -319,11 +321,9 @@ void agdeledgeimage(Agraph_t * g, Agedge_t * e, void *ignored)
     sn = agsubrep(g, t);
     del(g->e_seq, &sn->out_seq, out);
     del(g->e_id, &sn->out_id, out);
-    if (t != h) {
-	sn = agsubrep(g, h);
-	del(g->e_seq, &sn->in_seq, in);
-	del(g->e_id, &sn->in_id, in);
-    }
+    sn = agsubrep(g, h);
+    del(g->e_seq, &sn->in_seq, in);
+    del(g->e_id, &sn->in_id, in);
 #ifdef DEBUG
     for (e = agfstin(g,h); e; e = agnxtin(g,e))
 	assert(e != in);
diff --git a/lib/cgraph/graph.c b/lib/cgraph/graph.c
index bd4e6d17a..966abae49 100644
--- a/lib/cgraph/graph.c
+++ b/lib/cgraph/graph.c
@@ -191,6 +191,11 @@ int agisstrict(Agraph_t * g)
     return g->desc.strict;
 }
 
+int agissimple(Agraph_t * g)
+{
+    return (g->desc.strict && g->desc.no_loop);
+}
+
 int agdegree(Agraph_t * g, Agnode_t * n, int want_in, int want_out)
 {
     Agedge_t *e;
-- 
2.40.0