From f8ccbc01e43293d610973328dfcaf5f3753c9d92 Mon Sep 17 00:00:00 2001
From: Jean-Alexandre Barszcz <jalex_b@hotmail.com>
Date: Sat, 2 Dec 2017 02:53:08 -0500
Subject: digraph: Document a bad_edge error

---
 lib/stdlib/doc/src/digraph.xml | 4 ++++
 1 file changed, 4 insertions(+)

(limited to 'lib/stdlib/doc/src')

diff --git a/lib/stdlib/doc/src/digraph.xml b/lib/stdlib/doc/src/digraph.xml
index 5332d7aba5..db96beed6c 100644
--- a/lib/stdlib/doc/src/digraph.xml
+++ b/lib/stdlib/doc/src/digraph.xml
@@ -170,6 +170,10 @@
         <p>If the edge would create a cycle in
           an <seealso marker="#acyclic_digraph">acyclic digraph</seealso>,
           <c>{error,&nbsp;{bad_edge,&nbsp;<anno>Path</anno>}}</c> is returned.
+          If <c><anno>G</anno></c> already has an edge with value
+          <c><anno>E</anno></c> connecting a different pair of vertices,
+          <c>{error,&nbsp;{bad_edge,&nbsp;[<anno>V1</anno>,&nbsp;<anno>V2</anno>]}}</c>
+          is returned.
           If either of <c><anno>V1</anno></c> or <c><anno>V2</anno></c> is not
           a vertex of digraph <c><anno>G</anno></c>,
           <c>{error,&nbsp;{bad_vertex,&nbsp;</c><anno>V</anno><c>}}</c> is
-- 
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