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• egg

## graph-separators

Determine the separation vertices of a graph.

## Usage

(require-extension graph-separators)

## Documentation

A graph is said to have a separation vertex v (sometimes called an articulation point) if there exist vertices a and b, where a != b and b != v, and all paths connecting a and b pass through v. A graph which has a separation vertex is called separable, and one which has none is called non-separable.

### Procedures

[procedure] graph-separation-vertices:: G -> SEPARATORS * COMPONENTS

Computes the separation vertices of the given graph. Returns a list of separation vertices and a list of graph components that contain a separation vertex.

## Examples

```(require-extension srfi-1)
(require-extension digraph)
(require-extension graph-separators)

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

(define used-by
(list
(cons 'dax_h 'foo_cpp) (cons 'def_h 'foo_cpp) (cons 'xyz_h 'foo_cpp)
(cons 'foo_cpp 'libfoobar_a ) (cons 'foo_cpp 'libzigzag_a)
(cons 'libfoobar_a 'app) (cons 'libzigzag_a 'app)
))

(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 (list #f 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)

(graph-separation-vertices g)

```

### Author

Richard Kelsey; ported to Chicken by Ivan Raikov

### Version history

1.4
Documentation converted to wiki format
1.3
Ported to Chicken 4
1.0
Initial release

```Copyright by Richard Kelsey.

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