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Article contents:== Outdated egg! This is an egg for CHICKEN 4, the unsupported old release. You're almost certainly looking for [[/eggref/5/graph-scc|the CHICKEN 5 version of this egg]], if it exists. If it does not exist, there may be equivalent functionality provided by another egg; have a look at the [[https://wiki.call-cc.org/chicken-projects/egg-index-5.html|egg index]]. Otherwise, please consider porting this egg to the current version of CHICKEN. [[tags:egg]] == graph-scc Computes strongly-connected components (SCC) of a graph. [[toc:]] == Usage (require-extension graph-scc) == Documentation The graph-scc library computes the strongly connected components (SCC) of a graph, using Tarjan's algorithm, and a graph object that follows the API of e.g. the [[digraph|digraph egg]]. === SCC procedures <procedure>graph-scc-fold:: G F INITIAL -> STATE</procedure> SCC graph iterator; every SCC is represented as a list of nodes. the nodes in each SCC are folded together using the user-supplied function {{F}}, which is of the form {{LAMBDA SCC STATE}} == Examples ;; example adapted from graph example in the Boost library documentation (use srfi-1 digraph graph-scc) (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 'libfoobar_a 'dax_h) (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)))) ;; accumulate all SCC in a list (graph-scc-fold g (lambda (scc ax) (cons scc ax)) (list)) == About this egg === Author [[/users/ivan-raikov|Ivan Raikov]] === Version history ; 1.9 : Documentation converted to wiki format ; 1.8 : Ported to Chicken 4 ; 1.7 : Now using matchable extension ; 1.6 : Updated meta file for testbase ; 1.5 : Updated units tests to use testbase ; 1.4 : Build script updated for better cross-platform compatibility ; 1.3 : eggdoc documentation fix ; 1.2 : License upgrade to GPL v3. ; 1.1 : Added support for chicken-setup -test ; 1.0 : Initial release === License Copyright 2007-2010 Ivan Raikov and the Okinawa Institute of Science and Technology This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. A full copy of the GPL license can be found at <http://www.gnu.org/licenses/>. Description of your changes:

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