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graph-bfs

Breadth-first search in a graph.

Usage

(require-extension graph-bfs)

Documentation

The graph-bfs library is an implementation of breadth-first search on a graph object that follows the API of e.g. the digraph egg.

Breadth-first-search procedures

[procedure] graph-bfs-foreach:: G FNODE FEDGE ROOTS -> UNDEFINED

Breadth-first search iterator; given a list of initial nodes, ROOTS, the successors of each initial node are visited in breadth-first search order, and procedures FNODE and FEDGE are applied to each node or edge, respectively, as the graph is traversed. FNODE is of the form LAMBDA N -> _ where N is node number; and FEDGE is of the form LAMBDA EDGE where EDGE is a list of the form (I J INFO); I and J are the nodes defining the edge, and INFO is edge metadata.

[procedure] graph-bfs-fold:: G FNODE FEDGE ROOTS NODE-INIT EDGE-INIT -> NODE-STATE EDGE-STATE

Breadth-first search iterator with state; given a list of initial nodes, ROOTS, and initial node state and edge state, NODE-INIT and EDGE-INIT the successors of each initial node are visited in breadth-first search order, and procedures FNODE and FEDGE are applied to each node and the node state, or edge and the edge state, respectively, as the graph is traversed. FNODE is of the form LAMBDA N NODE-STATE -> NODE-STATE where N is node number, and NODE-STATE can be of arbitrary type and must of the same type as NODE-INIT. FEDGE is of the form LAMBDA EDGE EDGE-STATE where EDGE is a list of the form (I J INFO); I and J are the nodes defining the edge, and INFO is edge metadata; EDGE-STATE must be of the same type as EDGE-INIT

[procedure] graph-bfs-dist:: G ROOTS -> S32VECTOR * MAX-DIST

Breadth-first search distance; this procedure computes BFS maximum distance from a root node for all successors of the given initial nodes, and the maximum distance from root across all nodes traversed. The node distances are returned in an SRFI-4 vector of type S32VECTOR and MAX-DIST is the maximum distance computed.

Examples

 
;; example adapted from graph example in the Boost library documentation
(use srfi-1 digraph graph-bfs)

(define g (make-digraph 'depgraph "dependency graph"))

(define used-by
   (list 
     (cons 'dax_h 'foo_cpp) (cons 'dax_h 'bar_cpp) (cons 'dax_h 'yow_h)
     (cons 'yow_h 'bar_cpp) (cons 'yow_h 'zag_cpp) (cons 'boz_h 'bar_cpp)
     (cons 'boz_h 'zig_cpp) (cons 'boz_h 'zag_cpp) (cons 'zow_h 'foo_cpp)
     (cons 'foo_cpp 'foo_o) (cons 'foo_o 'libfoobar_a) 
     (cons 'bar_cpp 'bar_o) (cons 'bar_o 'libfoobar_a) 
     (cons 'libfoobar_a 'libzigzag_a) (cons 'zig_cpp 'zig_o) 
     (cons 'zig_o 'libzigzag_a) (cons 'zag_cpp 'zag_o) 
     (cons 'zag_o 'libzigzag_a) (cons 'libzigzag_a 'killerapp)))


(define node-list (delete-duplicates 
		   (concatenate (list (map car used-by) (map cdr used-by)))))

(define node-ids (list-tabulate (length node-list) values))
 
(for-each (lambda (i n) ((g 'add-node!) i n)) node-ids node-list)
(define node-map (zip node-list node-ids))

(for-each (lambda (e) 
	    (match e ((ni . nj) (let ((i (car (alist-ref ni node-map)))
				      (j (car (alist-ref nj node-map))))
				  ((g 'add-edge!) (list i j (format "~A->~A" ni nj)))))
		   (else (error "invalid edge " e))))
	  used-by)

(define roots (map car ((g 'roots))))

(graph-bfs-foreach g 
	   (lambda (n) (print (format "node ~A; " n)))
	   (lambda (e) (print (format "edge ~A; " e)))
	   roots)

(graph-bfs-fold g 
	       (lambda (n ax) (cons (list 'node n) ax)) 
	       (lambda (e ax) (cons (list 'edge e) ax)) 
	       roots (list) (list))

About this egg

Author

Ivan Raikov

Version history
1.12
Documentation converted to wiki format
1.11
Added digraph and test as test-dependencies
1.9
Ported to Chicken 4
1.8
Now using matchable extension
1.7
Unit tests updated to use testbase
1.6
Build script updated for better cross-platform compatibility
1.5
eggdoc documentation fix
1.4
License upgrade to GPL v3
1.3
Minor updates to the setup script
1.2
Added support for chicken-setup -test
1.1
Clarification in the section on graph-bfs-dist
1.0
Initial release