I just realized that I was looking at dependencies the wrong way (which is where I'm using this). So please ignore, the implementation is correct, I just made a mental typo :/ Christophe Poucet wrote:
Dear,
I think I have discovered a bug in Data.Graph. If one looks at the documentation it states:
Vertex = (Node, Node) An edge from the first vertex to the second. Ergo (i,j) => j is reachable from i
Then continuing, one reads that: topSort :: Graph -> [Vertex] A topological sort of the graph. The order is partially specified by the condition that a vertex /i/ precedes /j/ whenever /j/ is reachable from /i/ but not vice versa.
However if one tries to evaluate it, one gets:
print . G.components $ G.buildG (1,4) [(1,2), (1,3), (2,4), (2,3)] [1,3,2,4]
According to specification we have the graph (with arrows pointing down) 1 / \ | 3 |/ 2 | 4
Therefore one would expect [4,2,3,1].
Is this a bug in the documentation or the implementation?
With regards, Christophe
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