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Why do I find the following interaction counter-intuitive?

Graph[{L[1] \[DirectedEdge] R[1], L[2] \[DirectedEdge] R[2], R[1] \[DirectedEdge] L[2]}]
AcyclicGraphQ[%]

In the above L and R are undefined. (My actual code is in a module, and binds local L and R symbols, just to have a way of distinguishing the vertex classes in bipartite graphs.)

The answer I get is

False

At least usually. Is the function not defined for directed graphs? Is there a special DAGQ function that I haven't noticed?

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Is anything listed by ?*GraphQ? – cormullion Jan 27 at 16:27
Nothing that looks like a test for a DAG. Here is the output (from MMA8): AcyclicGraphQ DirectedGraphQ HamiltonianGraphQ SimpleGraphQ BipartiteGraphQ EmptyGraphQ IsomorphicGraphQ TreeGraphQ CompleteGraphQ EulerianGraphQ LoopFreeGraphQ UndirectedGraphQ ConnectedGraphQ GraphQ PathGraphQ WeightedGraphQ – Louis Jan 27 at 16:30
If none of those work, perhaps the answer is 'no'. – cormullion Jan 27 at 16:33
1  
What version of MM8 are you using? It's fixed in 8.0.1 and later. – halmir Jan 27 at 17:47
2  
I can't reproduce this in 8.0.1, 8.0.4 or 9.0.1. Did upgrading fix this problem for you? If yes, we should "close" this question. – Szabolcs Feb 11 at 21:30
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closed as too localized by Szabolcs, Sjoerd C. de Vries, m_goldberg, Oleksandr R., Yves Klett Feb 14 at 7:19

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