# [racket] Detecting cycle in directed graph

You may be interested in my graph package:
http://stchang.github.io/graph/graph.html
To install: raco pkg install graph
Example:
#lang racket
(require graph)
(define G (unweighted-graph/directed '((a b) (b c) (c d))))
(dag? G)
(add-directed-edge! G 'd 'a)
(dag? G)
=>
#t
#f
On Fri, Feb 14, 2014 at 7:42 AM, Erich Rast <erich at snafu.de> wrote:
>* I have a directed graph given as list of pairs ((from-node .
*>* to-node) ...) and need to detect whether adding a pair would create a
*>* cycle.
*>*
*>* Is there an easy way to do this already, e.g. some Planet package or
*>* snippet someone would like to share?
*>*
*>* I don't want to reinvent the wheel and this is not a homework question.
*>*
*>* Best,
*>*
*>* Erich
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*>* http://lists.racket-lang.org/users
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