From 9f60184ba78992422342b614d187f53880921de3 Mon Sep 17 00:00:00 2001
From: Cas Cremers <cas.cremers@gmail.com>
Date: Tue, 26 Apr 2011 11:49:40 +0200
Subject: [PATCH] Add isTermlistSetEqual code to compare sets that are encoded
 as lists.

---
 src/termlist.c | 17 +++++++++++++++++
 src/termlist.h |  1 +
 2 files changed, 18 insertions(+)

diff --git a/src/termlist.c b/src/termlist.c
index 430a109..1e4bcd5 100644
--- a/src/termlist.c
+++ b/src/termlist.c
@@ -762,6 +762,23 @@ termlistContained (const Termlist tlbig, Termlist tlsmall)
   return 1;
 }
 
+//! Check whether the element sets corresponding to two termlist are equal
+/**
+ * Currently this is a classical two-way containment test, but probably it can be done smarter.
+ */
+int
+isTermlistSetEqual (const Termlist tl1, const Termlist tl2)
+{
+  if (termlistContained (tl1, tl2))
+    {
+      if (termlistContained (tl2, tl1))
+	{
+	  return true;
+	}
+    }
+  return false;
+}
+
 //! Yield the result of f(x)
 /**
  * This function interpretes two termlists as the domain and range of a function,
diff --git a/src/termlist.h b/src/termlist.h
index 8507540..bdacb50 100644
--- a/src/termlist.h
+++ b/src/termlist.h
@@ -71,6 +71,7 @@ Term termLocal (const Term t, Termlist fromlist, Termlist tolist);
 Termlist termlistLocal (Termlist tl, const Termlist fromlist,
 			const Termlist tolist);
 int termlistContained (const Termlist tlbig, Termlist tlsmall);
+int isTermlistSetEqual (const Termlist tl1, const Termlist tl2);
 Term termFunction (Termlist fromlist, Termlist tolist, Term tx);
 Termlist termlistForward (Termlist tl);
 int termlistOrder (Termlist tl1, Termlist tl2);