Force special card after attack cards only

1 files changed, 8 insertions, 1 deletions

diff --git a/Card.hs b/Card.hs
index 64c74c8..98e76fe 100644
--- a/Card.hs
+++ b/Card.hs
@@ -47,8 +47,15 @@ isSpecial (Card _ rk)
   | rk `elem` [Two, Three, Seven, Jack, Queen] = True
   | otherwise = False
 
+-- | Check if card attacks.
+isAttack :: Card -> Bool
+isAttack (Card _ rk)
+  | rk `elem` [Two, Three] = True
+  | otherwise = False
+
 -- | Check if `card` is valid after `prev`.
+-- | If `prev` attacks, `card` must be special.
 isValid :: Card -> Card -> Bool
 isValid prev@(Card st' rk') card@(Card st rk) =
-    match && (not (isSpecial prev) || isSpecial card)
+    match && (not (isAttack prev) || isSpecial card)
         where match = (st == st') || (rk == rk')