graph: Add 'node-reachable-count'.
* guix/graph.scm (node-reachable-count): New procedure. * tests/graph.scm ("node-reachable-count"): New test.
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@ -39,6 +39,7 @@
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node-back-edges
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traverse/depth-first
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node-transitive-edges
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node-reachable-count
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%graphviz-backend
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graph-backend?
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@ -126,6 +127,13 @@ procedure that, given a node, returns its list of direct dependents; it is
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typically returned by 'node-edges' or 'node-back-edges'."
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(traverse/depth-first cons '() nodes node-edges))
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(define (node-reachable-count nodes node-edges)
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"Return the number of nodes reachable from NODES along NODE-EDGES."
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(traverse/depth-first (lambda (_ count)
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(+ 1 count))
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0
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nodes node-edges))
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;;;
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;;; Graphviz export.
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@ -275,4 +275,17 @@ edges."
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(return (lset= eq? (node-transitive-edges (list p2) edges)
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(list p1a p1b p0)))))))
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(test-equal "node-reachable-count"
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'(3 3)
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(run-with-store %store
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(let* ((p0 (dummy-package "p0"))
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(p1a (dummy-package "p1a" (inputs `(("p0" ,p0)))))
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(p1b (dummy-package "p1b" (inputs `(("p0" ,p0)))))
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(p2 (dummy-package "p2" (inputs `(("p1a" ,p1a) ("p1b" ,p1b))))))
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(mlet* %store-monad ((all -> (list p2 p1a p1b p0))
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(edges (node-edges %package-node-type all))
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(back (node-back-edges %package-node-type all)))
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(return (list (node-reachable-count (list p2) edges)
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(node-reachable-count (list p0) back)))))))
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(test-end "graph")
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