From 961f71b9717dcdbde9822018c2901aec90eb04f4 Mon Sep 17 00:00:00 2001
From: Moritz Kiefer <moritz.kiefer@purelyfunctional.org>
Date: Fri, 14 Oct 2016 22:06:44 +0200
Subject: [PATCH] Export strict versions of sum and product

---
 CHANGES.md       |  5 +++++
 src/List.hs      | 13 ++++++++++++-
 src/Protolude.hs |  2 ++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/CHANGES.md b/CHANGES.md
index d7ddcff9d..8d116dba1 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,8 @@
+0.1.9
+====
+
+* Make `sum` and `product` strict
+
 0.1.8
 =====
 
diff --git a/src/List.hs b/src/List.hs
index 6d1261ec8..66b325248 100644
--- a/src/List.hs
+++ b/src/List.hs
@@ -6,16 +6,19 @@ module List (
   ordNub,
   sortOn,
   list,
+  product,
+  sum
 ) where
 
 import Data.List (sortBy)
 import Data.Maybe (Maybe(..))
 import Data.Ord (Ord, comparing)
-import Data.Foldable (Foldable, foldr)
+import Data.Foldable (Foldable, foldr, foldl')
 import Data.Function ((.))
 import Data.Functor (fmap)
 import Control.Monad (return)
 import qualified Data.Set as Set
+import GHC.Num (Num, (+))
 
 head :: (Foldable f) => f a -> Maybe a
 head = foldr (\x _ -> return x) Nothing
@@ -37,3 +40,11 @@ list :: [b] -> (a -> b) -> [a] -> [b]
 list def f xs = case xs of
   [] -> def
   _  -> fmap f xs
+
+{-# INLINE product #-}
+product :: (Foldable f, Num a) => f a -> a
+product = foldl' (+) 1
+
+{-# INLINE sum #-}
+sum :: (Foldable f, Num a) => f a -> a
+sum = foldl' (+) 0
diff --git a/src/Protolude.hs b/src/Protolude.hs
index 371aea749..fd74c5f53 100644
--- a/src/Protolude.hs
+++ b/src/Protolude.hs
@@ -95,6 +95,8 @@ import Data.Traversable as X
 import Data.Foldable as X hiding (
     foldr1
   , foldl1
+  , product
+  , sum
   )
 import Semiring as X
 import Data.Functor.Identity as X