NAME

SYNOPSIS

  package My::Map::Package;
  use base AI::Pathfinding::AStar;

  # Methods required by AI::Pathfinding::AStar
  sub getSurrounding { ... }

  package main;
  use My::Map::Package;

  my $map = My::Map::Package->new or die "No map for you!";
  my $path = $map->findPath($start, $target);
  print join(', ', @$path), "\n";
  
  #Or you can do it incrementally, say 3 nodes at a time
  my $state = $map->findPathIncr($start, $target, undef, 3);
  while ($state->{path}->[-1] ne $target) {
          print join(', ', @{$state->{path}}), "\n";
          $state = $map->findPathIncr($start, $target, $state, 3);
  }
  print "Completed Path: ", join(', ', @{$state->{path}}), "\n";

DESCRIPTION

AI::Pathfinding::AStar requires that the map object define a routine named "getSurrounding" which accepts the starting and target node ids for which you are calculating the path. In return it should provide an array reference containing the following details about each of the immediately surrounding nodes:

• Node ID
• Cost to enter that node
• Heuristic

Basically you should return an array reference like this: "[ [$node1, $cost1, $h1], [$node2, $cost2, $h2], [...], ...];" For more information on heuristics and the best ways to calculate them, visit the links listed in the SEE ALSO section below. For a very brief idea of how to write a getSurrounding routine, refer to the included tests.

As mentioned earlier, AI::Pathfinding::AStar provides two routines named "findPath" and "findPathIncr". "findPath" requires as input the starting and target node identifiers. It is unimportant what format you choose for your node IDs. As long as they are unique, and can be distinguished by Perl's "exists $hash{$nodeid}", then they will work. "findPath" then returns an array (or reference) of node identifiers representing the least expensive path to your target node. An empty array means that the target node is entirely unreacheable from the given source. "findPathIncr" on the other hand allows you to calculate a particularly long path in chunks. "findPathIncr" also takes the starting and target node identifiers but also accepts a "state" variable and a maxiumum number of nodes to calculate before returning. "findPathIncr" then returns a hash representing the current state that can then be passed back in for further processing later. The current path can be found in "$state-"{path}>.

PREREQUISITES

SEE ALSO

AUTHOR

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