Create GOL.Rule

GOL/Rule.hs

@@ -0,0 +1,26 @@
+module GOL.Rule where
+
+-- | The rule of a Conway's Game of Life simulation
+-- describes how a cell changes based on its surrounding
+-- cells. The official GOL uses one standard rule, but
+-- this engine allows for an arbitrary rule to be applied.
+--
+-- A rule consists of two predicates that take a value
+-- in the range [0..8], the count of alive cells neighboring
+-- the current cell, and returns whether that cell will be
+-- alive in the next generation.
+data Rule = Rule
+  {
+    -- | A predicate deciding if an alive cell
+    -- will be alive in the next generation.
+    survive :: Int -> Bool,
+    -- | A predicate deciding if a dead cell
+    -- will be alive in the next generation.
+    birth :: Int -> Bool
+  }
+
+
+-- | The standard GOL rule (S23/B3).
+standardRule :: Rule
+standardRule = Rule (`elem` [2,3]) (== 3)
+