Summary

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	File:     graphpak.icn

	Subject:  Procedures for manipulating directed graphs

	Author:   Ralph E. Griswold

	Date:     May 2, 2001

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   This file is in the public domain.

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  The procedures here use sets to represent directed graphs.  See
  The Icon Programming Language, second edition, pp. 195-198.

  A value of type "graph" has two components: a list of nodes and
  a two-way lookup table.  The nodes in turn contain pointers to
  other nodes.  The two-way table maps a node to its name and
  vice-versa.

  Graph specifications are give in files in which the first line
  is a white-space separated list of node names and subsequent lines
  give the arcs, as in

	Tucson Phoenix Bisbee Douglas Flagstaff
	Tucson->Phoenix
	Tucson->Bisbee
	Bisbee->Bisbee
	Bisbee->Douglas
	Douglas->Phoenix
	Douglas->Tucson

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This file is part of the (main) package.

closure(node, close)

: transitive closure of graph

read_graph(f)

: read graph

write_graph(g, f)

: write graph

graph(nodes, lookup)