1 files changed, 12 insertions, 0 deletions
diff --git a/src/Mahjong/Pai.hs b/src/Mahjong/Pai.hs
index 08115e9..067196e 100644
--- a/src/Mahjong/Pai.hs
+++ b/src/Mahjong/Pai.hs
@@ -1,6 +1,9 @@
 module Pai where
 
 import Data.Char (toUpper)
+import Data.List (sort)
+import Data.Maybe
+import Control.Monad
 
 data MCol = Man | Pin | Sou | Cha
     deriving (Eq,Ord)
@@ -27,4 +30,13 @@ isCha c@(MCard col n) = (col == Cha)
 isLaoTou c@(MCard col n) = ((n == 1) || (n == 9)) && (not $ isCha c)
 is19 c@(MCard col n) = (isCha c) || (isLaoTou c)
 
+orderedPai = sort $ [MCard c n | c<-[Man,Pin,Sou], n <-[1..9]] ++ (map (MCard Cha) [1..7])
 
+nextPai p = if xs /= [] then Just $ head xs
+            else Nothing
+    where (x:xs) = dropWhile (/= p) orderedPai
+
+nextPai' p@(MCard c n) = do
+    nx <- nextPai p
+    guard ((c /= Cha) && (n /= 9))
+    return nx