refactor: move parser functions into Utils

src/Day3/Part1.idr

@@ -4,13 +4,10 @@ import Data.Either
 import Data.Maybe
 import Data.String
 import Data.String.Parser
+import Utils
 
 --- PARSING
 
-export
-scan : Monad m => ParseT m a -> ParseT m a
-scan p = many (requireFailure p *> skip (satisfy (const True))) *> p
-
 export
 mul : Parser Integer
 mul = do

src/Utils.idr

@@ -2,9 +2,29 @@ module Utils
 
 import Data.Maybe
 import Data.String
+import Data.String.Parser
 
 %default total
 
 export
 parseNat : String -> Maybe Nat
 parseNat = map cast . filter (> 0) . parseInteger
+
+
+export
+lookahead : Functor m => ParseT m a -> ParseT m a
+lookahead p = P $ \s => map (\case
+                                OK r _ => OK r s
+                                Fail i err => Fail i err)
+                            (p.runParser s)
+export covering
+until : Monad m => ParseT m a -> ParseT m ()
+until p = skip $ many (requireFailure p *> skip (satisfy (const True)))
+
+export covering
+scan : Monad m => ParseT m a -> ParseT m a
+scan p = until p *> p
+
+export covering
+scanWhile : Monad m => ParseT m a -> ParseT m b -> ParseT m b
+scanWhile w p = many (lookahead w *> requireFailure p *> skip (satisfy (const True))) *> p