From 79abc9ea961d6e921e51187971b87cd0939be11b Mon Sep 17 00:00:00 2001
From: Jean-Paul Calderone <exarkun@twistedmatrix.com>
Date: Thu, 29 Aug 2019 19:39:47 -0400
Subject: [PATCH] fmap is more constrained than liftM
Therefore this approach is preferable
---
src/PaymentServer/Persistence.hs | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/src/PaymentServer/Persistence.hs b/src/PaymentServer/Persistence.hs
index 4163cad..eea14b4 100644
--- a/src/PaymentServer/Persistence.hs
+++ b/src/PaymentServer/Persistence.hs
@@ -82,8 +82,8 @@ instance VoucherDatabase MemoryVoucherDatabase where
return ()
redeemVoucher Memory{ paid = paid, redeemed = redeemed } voucher fingerprint = do
- unpaid <- (liftM $ Set.notMember voucher) . readIORef $ paid
- existingFingerprint <- (liftM $ Map.lookup voucher) . readIORef $ redeemed
+ unpaid <- Set.notMember voucher <$> readIORef paid
+ existingFingerprint <- Map.lookup voucher <$> readIORef redeemed
case (unpaid, existingFingerprint) of
(True, _) ->
return $ Left NotPaid
--
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