From bb9e8620371b8d6b45f343867729d638a3c0eed4 Mon Sep 17 00:00:00 2001
From: Mats Rydberg <mats@neotechnology.com>
Date: Wed, 1 Mar 2017 15:53:14 +0100
Subject: [PATCH] Add example for CIR-2017-172

References #172
---
 cip/1.accepted/CIP2016-12-14-Constraint-syntax.adoc | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/cip/1.accepted/CIP2016-12-14-Constraint-syntax.adoc b/cip/1.accepted/CIP2016-12-14-Constraint-syntax.adoc
index f2680afda1..2745d1f961 100644
--- a/cip/1.accepted/CIP2016-12-14-Constraint-syntax.adoc
+++ b/cip/1.accepted/CIP2016-12-14-Constraint-syntax.adoc
@@ -217,6 +217,16 @@ FOR (p:Programmer)
 REQUIRE p:Person
 ----
 
+Assuming a function `acyclic()` that takes a path as argument and returns `true` if and only if the same node does not appear twice in the path, otherwise `false`, we may express:
+
+.Constraint example from CIR-2017-172
+[source, cypher]
+----
+CREATE CONSTRAINT enforce_dag_acyclic_for_R_links
+FOR p = ()-[:R*]-()
+REQUIRE acyclic(p)
+----
+
 === Interaction with existing features
 
 The main interaction between the constraints and the rest of the language occurs during updating statements.