= astar_heuristic

This class is a default implementation of the
xref:visitors/AStarHeuristic.adoc[AStarHeuristic] concept. It implements a
"zero" heuristic -- a heuristic function that returns a cost of zero
regardless of the vertex it is passed.

== Model of

xref:visitors/AStarHeuristic.adoc[AStarHeuristic]

== Template Parameters

[cols=",,",options="header",]
|===
|Parameter |Description |Default
|`Graph` |The type of the graph being searched. |

|`CostType` |A type that can be used with the `compare` and `combine`
functions passed to A*. Typically an integer or floating point type.
|
|===

== Where Defined

`boost/graph/astar_search.hpp`

== Member Functions

This class implements the single member function required by
xref:visitors/AStarHeuristic.adoc[AStarHeuristic]:

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|===
|Function |Description
|` CostType operator()(graph_traits<Graph>::vertex_descriptor u); `
|Called for the target of every out edge of a vertex being examined.
Returns the cost, estimated by the heuristic, from vertex `u` to a goal.
|===
