import java.util.Stack;
import java.io.FileInputStream;
import java.io.FileOutputStream;

// the data structure for the graph searching
// method of edge linking.

Graph = "{" List(GraphNode) *l "}" *l.
GraphNode : EndNode | IntermediateNode common EdgeLoc NodeData .
EndNode : SourceNode | TargetNode common .
NodeData = <cost> int [ PathData ] .
PathData = "path" <pathCost> int <path> GraphNode.
IntermediateNode = "inode" [NodeList] *l.
SourceNode = "src" [NodeList] *l.
TargetNode = *l "target" *l.

NodeList = "list" <graphNodeList> ListP(GraphNode).

PixelCoord = "(" <x> int "," <y> int ")".
EdgeLoc = <left> PixelCoord <right> PixelCoord.

List(S) ~ { S }.
ListP(S) ~ "(" S {"," S } ")" .

Main = <s> String.


//////////////////////////////////////////////////////////
// datastructures for generating the graph edges and nodes
// from the source and target points.

GraphGenerator = <src> PixelCoord <target> PixelCoord [ LineEquation ] [<generatedGraph> Graph ].
LineEquation = <Slope> float <Constant> float <direction> int.


//////////////////////////////////////////////////////////
// File IO classes

Image = <height> int <width> int <maxPixelVal> int.