feat:Implemented Harary graph creation.

Author: antononcube

lib/Graph/Classes.rakumod

@@ -7,6 +7,7 @@ sub EXPORT {
     use Graph::CompleteKaryTree;
     use Graph::Cycle;
     use Graph::Grid;
+    use Graph::Harary;
     use Graph::HexagonalGrid;
     use Graph::Hypercube;
     use Graph::Indexed;
@@ -29,6 +30,7 @@ sub EXPORT {
             'Graph::CompleteKaryTree' => Graph::CompleteKaryTree,
             'Graph::Cycle' => Graph::Cycle,
             'Graph::Grid' => Graph::Grid,
+            'Graph::Harary' => Graph::Harary,
             'Graph::HexagonalGrid' => Graph::HexagonalGrid,
             'Graph::Hypercube' => Graph::Hypercube,
             'Graph::Indexed' => Graph::Indexed,

lib/Graph/Harary.rakumod

@@ -0,0 +1,45 @@
+use v6.d;
+
+use Graph;
+
+class Graph::Harary is Graph {
+    has Int:D $.k is required;
+    has Int:D $.n is required;
+
+    submethod BUILD(:$!k!, :$!n!, Str:D :$prefix = '') {
+
+        for ^$!n -> $i {
+            for (1 ... $!k div 2) -> $j {
+                self.edge-add($prefix ~ $i.Str, $prefix ~ (($i + $j) % $!n).Str, :!directed);
+                self.edge-add($prefix ~ $i.Str, $prefix ~ (($i - $j) % $!n).Str, :!directed);
+            }
+        }
+
+        if $!k !%% 2 {
+            if $!n %% 2 {
+                for ^($!n div 2) -> $i {
+                    self.edge-add($prefix ~ $i.Str, $prefix ~ ($i + $!n div 2).Str, :!directed);
+                }
+            } else {
+                for ^(($!n - 1) div 2 + 1) -> $i {
+                    self.edge-add($prefix ~ $i.Str, $prefix ~ ($i + ($!n + 1) div 2).Str, :!directed);
+                }
+                self.edge-add($prefix ~ '0', $prefix ~ (($!n - 1) div 2).Str, :!directed);
+                self.edge-add($prefix ~ '0', $prefix ~ (($!n + 1) div 2).Str, :!directed)
+            }
+        }
+
+        # Same as Circulant
+        self.vertex-coordinates =
+                self.vertex-list.map({ my $i = $_.subst($prefix).Int - 1; $_ => [cos(2 * pi / $!n * $i), sin(2 * pi / $!n * $i)]}).Hash;
+    }
+
+    multi method new(Int:D $k, Int:D $n, Str:D :$prefix = '') {
+        self.bless(:$k, :$n, :$prefix);
+    }
+
+    multi method new(Int:D :$n, Int:D :$k, Str:D :$prefix = '') {
+        self.new($k, $n, :$prefix);
+    }
+}
+