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graph: Expose 'traverse/depth-first'.

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* guix/graph.scm (traverse/depth-first): New procedure, based on code
formerly in 'node-transitive-edges'.
(node-transitive-edges): Rewrite in terms of it.
This commit is contained in:
Ludovic Courtès 2016-05-23 22:31:59 +02:00
parent 9a6beb3b7f
commit 623e4df42a
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1 changed files with 15 additions and 7 deletions
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22
guix/graph.scm
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@ -37,6 +37,7 @@ (define-module (guix graph)
node-edges
node-back-edges
traverse/depth-first
node-transitive-edges
%graphviz-backend
@ -99,13 +100,13 @@ (define (node-back-edges type nodes)
(lambda (source target edges)
(vhash-consq target source edges))))
(define (node-transitive-edges nodes node-edges)
"Return the list of nodes directly or indirectly connected to NODES
according to the NODE-EDGES procedure. NODE-EDGES must be a one-argument
procedure that, given a node, returns its list of direct dependents; it is
typically returned by 'node-edges' or 'node-back-edges'."
(define (traverse/depth-first proc seed nodes node-edges)
"Do a depth-first traversal of NODES along NODE-EDGES, calling PROC with
each node and the current result, and visiting each reachable node exactly
once. NODES must be a list of nodes, and NODE-EDGES must be a one-argument
procedure as returned by 'node-edges' or 'node-back-edges'."
(let loop ((nodes (append-map node-edges nodes))
(result '())
(result seed)
(visited (setq)))
(match nodes
(()
@ -115,9 +116,16 @@ (define (node-transitive-edges nodes node-edges)
(loop tail result visited)
(let ((edges (node-edges head)))
(loop (append edges tail)
(cons head result)
(proc head result)
(set-insert head visited))))))))
(define (node-transitive-edges nodes node-edges)
"Return the list of nodes directly or indirectly connected to NODES
according to the NODE-EDGES procedure. NODE-EDGES must be a one-argument
procedure that, given a node, returns its list of direct dependents; it is
typically returned by 'node-edges' or 'node-back-edges'."
(traverse/depth-first cons '() nodes node-edges))
;;;
;;; Graphviz export.