formal languages

Logic/Language.hs

@@ -0,0 +1,15 @@
+module Logic.Language where
+
+-- Formal language (/grammar/production system/whatever)
+class (Eq symbol, Show symbol) => Language symbol where
+  -- If Haskell had dependent types this could be generalized.
+  -- For now the languages I want to make use at most up to infer3.
+  infer0 :: [[symbol]]
+  infer1 :: [[symbol] -> [[symbol]]]
+  infer2 :: [[symbol] -> [symbol] -> [[symbol]]]
+  infer3 :: [[symbol] -> [symbol] -> [symbol] -> [[symbol]]]
+
+-- Convenience newtype so strings are less ugly
+newtype Seq symbol = Seq [symbol]
+instance Show a => Show (Seq a) where
+  show (Seq xs) = concat $ map show xs