How to build a Weighted Graph with Ruby's RGL or GRATR to perform Dijkstra's algorithm?

I would like to see an example of a Dijkastra search algorithm for a graph built using Ruby's RGL (http://rgl.rubyforge.org/) or GRATR (http://rubyforge.org/projects/gratr/).

I know开发者_如何学C GRATR has Dijkastra support but I'm not really sure how to go about using it, any help would be appreciated.

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One of these should help:

http://snippets.dzone.com/posts/show/7331
http://snippets.dzone.com/posts/show/6100
http://github.com/dbrady/dijkstra

This is an example of dijkstra in GRATR
http://gratr.rubyforge.org/svn/examples/graph_self.rb