NAME
Graph::Traverse - A traverse() method for the Graph module.
SYNOPSIS
use Graph;
use Graph::Traverse;
my $g = Graph->new();
$g->add_path(qw(A B1 B2 C));
$g->add_path(qw(A D1 D2 C));
my $vertices = $g->traverse('A');
# $vertices now is ['B', 'C', 'D'] or some combination thereof
my $paths = $g->traverse('A', {hash => 1});
# $paths contains a hash like this:
# { 'B1' => { 'vertex' => 'B1',
# 'path' => ['A', 'B1'],
# 'weight' => 1 },
# 'B2' => { 'vertex' => 'B2',
# 'path' => ['A', 'B1', 'B2'],
# 'weight' => 2 },
# 'D1' => { 'vertex' => 'D1',
# 'path' => ['A', 'D1'],
# 'weight' => 1 },
# 'D2' => { 'vertex' => 'D2',
# 'path' => ['A', 'D1', 'D2'],
# 'weight' => 2 },
# 'C' => { 'vertex' => 'C',
# 'path' => ['A', 'D1', 'D2', 'C'],
# 'weight' => 3 }
# }
METHODS
The only method resides in the Graph package (not Graph::Traverse) so
that any descendant of Graph can call it.
traverse ( $start_vertex, [ \%opts ] );
traverse ( \@start_vertices , [ \%opts ] );
Traverses edges from the start vertex (or vertices) [either a single
vertex's name, or an array of vertex names, may be passed], finding
adjacent vertices using the 'next' function (by default, 'successors'),
until either a maximum accumulated edge weight ('max' option, if given)
is exceeded (by default using the 'weight' attribute, or specify an
'attribute'), or until a callback function ('cb') returns a nonzero
value. By default, the return value is the list of vertices encountered
in the search.
Note that as we traverse the graph, we may encounter the same vertex
several times, but only the shortest path (lowest weight) will be
retained.
The following options are available:
hash
Use with a nonzero value to return a hash where keys are vertex
names, and values are as follows:
vertex
The current (found) vertex.
path
The path from the starting vertex (or one of the starting vertices)
to the current vertex.
weight
The accumulated weight from the starting vertex. By default, each
edge's 'weight' attribute is used; see options 'attribute' and
'vertex'.
terminal
If the 'cb' option is provided, this is the value that the function
returned at this vertex.
attribute
The edge (or vertex) attribute to use as each edge's (vertex's)
weight.
max
A maximum weight, above which the traversal will terminate. If
undefined, the traversal continues either until there are no more
vertices to search (e.g., no further successors), or until the
callback function (if any) returns a nonzero value.
default
The default weight value for an edge (or vertex).
vertex
If this option is true, accumulate the weight of each successive
vertex, rather than the weights of the edges.
cb
A callback function which is called for each discovered vertex. It is
called as follows:
&$callback($self, $vertex, $weight, $opts))
Where the arguments are: the Graph object itself; the name of the
current vertex; the accumulated weight at that vertex; and the
options hash as passed to traverse().
If the callback function returns a nonzero value, the successors (or
whatever vertices might be returned by the 'next' function) beyond
the current vertex are not searched. The callback's value at each
vertex will be saved in the returned hash, if any.
Note that multiple paths to a given vertex may cause multiple
callbacks with varying weights.
all
Useful only when 'hash' is true and a 'cb' function is given. If
'all' is omitted, or is set to a nonzero value, the returned hash
will include all vertices which were encountered in the traversal. If
'all' has a nonzero value, only the vertices for which the callback
returned a nonzero value will be added to the hash.
weights
Use option 'weights', with a nonzero value, to obtain a returned list
of vertex=>weight_value.
next
The name of a Graph method to find adjacent vertices. By default,
'successors' is used; alternate useful values include 'predecessors'
and 'neighbors'.
AUTHOR
William Lindley
COPYRIGHT
Copyright 2019, William Lindley
LICENSE
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
SEE ALSO
Graph