First stab at A*

.travis.yml

@@ -11,3 +11,4 @@ script:
   - dub test
   - (cd "examples/Connected Components" && dub build)
   - (cd "examples/Dijkstra" && dub build)
+  - (cd "examples/Astar Cities" && dub build)

examples/Astar Cities/dub.sdl

@@ -0,0 +1,6 @@
+name "astar-cities"
+description "An example illustrating an A* search."
+copyright "Copyright © 2016, Trent Clarke"
+license "BSL-1.0"
+authors "Trent Clarke"
+dependency "anansi" version="master" path="../../"

examples/Astar Cities/source/app.d

@@ -0,0 +1,123 @@
+/**
+ * An example using the anansi A* search algorithm. Ported from the
+ * boost graph library's example.
+ */
+import anansi,
+       anansi.algorithms.astar;
+import std.math : sqrt;
+import std.algorithm : reverse;
+import std.stdio : write, writeln;
+import std.container;
+
+/**
+ * The city data associated wth a given vertex. 
+ */
+struct City {
+    this(string n, real latitude, real longitude) {
+        name = n;
+        lat = latitude;
+        lng = longitude;
+    }
+
+    string name;
+    real lat;
+    real lng;
+}
+
+alias Graph = AdjacencyList!(VecS, VecS, DirectedS, City, real);
+alias Vertex = Graph.VertexDescriptor;
+
+/**
+ * An exception type that signals that a path through the graph has been found.
+ */
+class FoundTarget : Throwable {
+    this() { super("found it"); }
+}
+
+struct AStarGoalVisitor {
+    mixin NullAstarVisitor!Graph;
+
+    Vertex _target;
+
+    this(Vertex target) {
+        _target = target;
+    }
+
+    void examineVertex(ref const(Graph) g, Vertex v) {
+        if (v == _target) {
+            throw new FoundTarget;
+        }
+    }
+}
+
+
+void main() {
+    Graph g;
+
+    auto troy          = g.addVertex(City("Troy",          42.73, 73.68));
+    auto lake_placid   = g.addVertex(City("Lake Placid",   44.28, 73.99));
+    auto plattsborough = g.addVertex(City("Plattsborough", 44.70, 73.46));
+    auto massena       = g.addVertex(City("Massena",       44.93, 74.89));
+    auto watertown     = g.addVertex(City("Watertown",     43.97, 75.91));
+    auto utica         = g.addVertex(City("Utica",         43.10, 75.23));
+    auto syracuse      = g.addVertex(City("Syracuse",      43.04, 76.14));
+    auto rochester     = g.addVertex(City("Rochester",     43.17, 77.61));
+    auto buffalo       = g.addVertex(City("Buffalo",       42.89, 78.86));
+    auto ithaca        = g.addVertex(City("Ithaca",        42.44, 76.50));
+    auto binghamton    = g.addVertex(City("Binghamon",     42.10, 75.91));
+    auto woodstock     = g.addVertex(City("Woodstock",     42.04, 74.11));
+    auto new_york      = g.addVertex(City("New York",      40.67, 73.94));
+
+    g.addEdge(troy,          utica,          93);
+    g.addEdge(troy,          lake_placid,   134);
+    g.addEdge(troy,          plattsborough, 143);
+    g.addEdge(lake_placid,   plattsborough,  65);
+    g.addEdge(plattsborough, massena,       115);
+    g.addEdge(lake_placid,   massena,       113);
+    g.addEdge(massena,       watertown,     117);
+    g.addEdge(watertown,     utica,         116);
+    g.addEdge(watertown,     syracuse,       74);
+    g.addEdge(utica,         syracuse,       56);
+    g.addEdge(syracuse,      rochester,      84);
+    g.addEdge(rochester,     buffalo,        73);
+    g.addEdge(syracuse,      ithaca,         69);
+    g.addEdge(ithaca,        binghamton,     70);
+    g.addEdge(ithaca,        rochester,     116);
+    g.addEdge(binghamton,    troy,          147);
+    g.addEdge(binghamton,    woodstock,     173);
+    g.addEdge(binghamton,    new_york,      183);
+    g.addEdge(syracuse,      binghamton,     74);
+    g.addEdge(woodstock,     troy,           71);
+    g.addEdge(woodstock,     new_york,      124);
+
+    auto src = woodstock;
+    auto target = watertown;
+
+    real heuristic(Vertex v) {
+        auto dx = g[target].lng - g[v].lng;
+        auto dy = g[target].lat - g[v].lat;
+        return sqrt(dx * dx + dy * dy);
+    }
+
+    auto predecessor = new Graph.VertexDescriptor[g.vertexCount];
+
+    try {
+        aStarSearch(g,
+                    src,
+                    &heuristic,
+                    g,
+                    predecessor,
+                    AStarGoalVisitor(target));
+    }
+    catch(FoundTarget) {
+        writeln("Found a path");
+        auto path = extractPath(predecessor, target);
+
+        write(g[path[0]].name);
+        foreach (n; path[1..$]) {
+            write(" -> ", g[n].name);
+        }
+
+        writeln("");
+    }
+}

examples/Connected Components/source/app.d

@@ -1,5 +1,5 @@
 /**
- * An example using the anansi connected compomemt finder. Ported from the 
+ * An example using the anansi connected compomemt finder. Ported from the
  * boost graph library's example.
  */
 
@@ -20,7 +20,7 @@ void main() {
     graph.addEdge(b, e);
     graph.addEdge(e, a);
     graph.addEdge(c, f);
-    
+
     size_t[6] componentMap;
     auto nComponents = connectedComponents(graph, componentMap);
 

examples/Dijkstra/source/app.d

@@ -1,7 +1,7 @@
 
 /**
  * Copyright 2014 Trent Clarke.
- * 
+ *
  * Distributed under the Boost Software License, Version 1.0. (See
  * copy at http://www.boost.org/LICENSE_1_0.txt)
  */
@@ -12,7 +12,7 @@ import std.stdio;
 void main()
 {
     alias Graph = AdjacencyList!(VecS, VecS, DirectedS, char, string);
-	
+
     Graph graph;
     auto a = graph.addVertex('a');
     auto b = graph.addVertex('b');
@@ -35,13 +35,13 @@ void main()
     auto colourMap = new Colour[graph.vertexCount];
     auto distance = new real[graph.vertexCount];
     auto predecessor = new Graph.VertexDescriptor[graph.vertexCount];
-    dijkstraShortestPaths(graph, a, weight, predecessor, 
-                          NullDijkstraVisitor!Graph(), 
+    dijkstraShortestPaths(graph, a, weight, predecessor,
+                          NullDijkstraVisitor!Graph(),
                           colourMap,
                           distance);
 
     foreach(v; graph.vertices) {
-        writeln(graph[v], " - Distance: ", distance[v], 
+        writeln(graph[v], " - Distance: ", distance[v],
 	                  ", Predecessor: ", graph[predecessor[v]]);
     }
 }

readme.md

@@ -8,7 +8,7 @@ This first pass will probably be a pretty simple translation of (bits of) the BG
 
 **Q**: Why another graph handling library?
 
-**A**: Because the only available graph handling library in the Dub package registry was GPL licensed, and I thought it might be nice to have a graph library that people can use in commercial code. Don't get me wrong; [the dgraph library](http://code.dlang.org/packages/dgraph) is awesome, and got me out of a hole in a personal project. It is also a hell of a lot simpler to use than this. I just wanted the option. 
+**A**: Because the only available graph handling library in the Dub package registry was GPL licensed, and I thought it might be nice to have a graph library that people can use in commercial code. Don't get me wrong; [the dgraph library](http://code.dlang.org/packages/dgraph) is awesome, and got me out of a hole in a personal project. It is also a hell of a lot simpler to use than this. I just wanted the option.
 
 **Q**: Why "Anansi"?
 
@@ -34,7 +34,7 @@ void fn() {
   auto a = g.addVertex('a');
   auto b = g.addVertex('b');
   g.addEdge(a, b, "a -> b");
-  
+
   // now dow something interesting with your graph
   for(v; g.vertices) {
     writeln("Hi from vertex ", g[v]);