From 0d74c4bcfaedfc5ba517406010bea1497473c7e7 Mon Sep 17 00:00:00 2001
From: Neil Smith <neil.git@njae.me.uk>
Date: Mon, 25 Dec 2017 21:03:43 +0000
Subject: [PATCH] Tidied the parser a bit

---
 src/advent25/advent25.hs | 50 +++++++++++++++++++++-------------------
 1 file changed, 26 insertions(+), 24 deletions(-)

diff --git a/src/advent25/advent25.hs b/src/advent25/advent25.hs
index 656c775..aa3ff4d 100644
--- a/src/advent25/advent25.hs
+++ b/src/advent25/advent25.hs
@@ -90,39 +90,41 @@ lexeme = L.lexeme sc
 integer = lexeme L.integer
 symbol = L.symbol sc
 fullstop = symbol "."
+colon = symbol ":"
+dash = symbol "-"
 
-commandP = between (symbol "-") fullstop
+machineDescriptionP = machineify <$> startStateP <*> stepsP <*> manyStateRulesP
+    where machineify initial limit rules = 
+            ( emptyMachine { tState = initial, stepsRemaining = limit }
+            , rules
+            )
 
-writeValueP = (symbol "1" *> pure True) <|> (symbol "0" *> pure False)
-writeP = commandP ((symbol "Write the value") *> writeValueP)
+startStateP = (symbol "Begin in state") *> stateP <* fullstop
+stepsP =  (symbol "Perform a diagnostic checksum after") *> integer <* (symbol "steps") <* fullstop
+            
+manyStateRulesP = M.unions <$> (stateRulesP `sepBy` space)
 
-directionP = (symbol "left" *> pure -1) <|> (symbol "right" *> pure 1)
-tapeMovementP = commandP ((symbol "Move one slot to the") *> directionP)
+stateRulesP = rulify <$> stateDefP <*> (stateWhenP `sepBy` space)
+    where rulify s ts = M.fromList $ map (\(v, t) -> ((s, v), t)) ts
 
-newStateP = commandP ((symbol "Continue with state") *> (some letterChar))
+stateWhenP = (,) <$> currentValueP <*> stateTransitionP
+    
+stateDefP = (symbol "In state") *> stateP <* colon
+currentValueP = (symbol "If the current value is") *> writeValueP <* colon
 
 stateTransitionP = stify <$> writeP <*> tapeMovementP <*> newStateP
     where stify w t s = StateTransition {writeValue = w, newState = s, tapeMovement = t}
-    
-currentValueP = (symbol "If the current value is") *> writeValueP <* (symbol ":")
-    
-stateWhenP = (,) <$> currentValueP <*> stateTransitionP
-    
-stateDefP = (symbol "In state") *> (some letterChar) <* (symbol ":")
-    
-stateRulesP = rulify <$> stateDefP <*> (stateWhenP `sepBy` space)
-    where rulify s ts = M.fromList $ map (\(v, t) -> ((s, v), t)) ts
-   
-manyStateRulesP = M.unions <$> (stateRulesP `sepBy` space)
 
-startStateP = (symbol "Begin in state") *> (some letterChar) <* fullstop
-stepsP =  (symbol "Perform a diagnostic checksum after") *> integer <* (symbol "steps") <* fullstop
+commandP = between dash fullstop
+
+writeP = commandP ((symbol "Write the value") *> writeValueP)
+tapeMovementP = commandP ((symbol "Move one slot to the") *> directionP)
+newStateP = commandP ((symbol "Continue with state") *> stateP)
+
+stateP = some letterChar
+directionP = (symbol "left" *> pure -1) <|> (symbol "right" *> pure 1)
+writeValueP = (symbol "1" *> pure True) <|> (symbol "0" *> pure False)
 
-machineDescriptionP = machineify <$> startStateP <*> stepsP <*> manyStateRulesP
-    where machineify initial limit rules = 
-            ( emptyMachine { tState = initial, stepsRemaining = limit }
-            , rules
-            )
 
 successfulParse :: Text -> (Machine, Rules)
 successfulParse input = 
-- 
2.34.1