From 6f92e70575a76771dc82662ce28ed0a91e6b84ae Mon Sep 17 00:00:00 2001
From: Dmitry Astapov <dastapov@gmail.com>
Date: Tue, 28 Nov 2017 01:22:44 +0000
Subject: [PATCH] lib: remove needless numeric comparisons in bal/bs

accountsFromPostings is currently doing excessive work when adding up
postings in each account. It sorts (accountName, amount) tuples which
cause amounts in them to be compared. There is no need to look at amount
here at all since subsequent summing up and counting does not depend on
order. It is enough to sort by accountname only.

Went through similar pieces of code, made them all look uniform.
---
 hledger-lib/Hledger/Data/Account.hs | 10 +++++-----
 hledger-lib/Hledger/Data/Journal.hs |  4 ++--
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/hledger-lib/Hledger/Data/Account.hs b/hledger-lib/Hledger/Data/Account.hs
index 64cfbaf0a..e1dc82415 100644
--- a/hledger-lib/Hledger/Data/Account.hs
+++ b/hledger-lib/Hledger/Data/Account.hs
@@ -10,6 +10,7 @@ account, and subaccounting-excluding and -including balances.
 module Hledger.Data.Account
 where
 import Data.List
+import Data.List.Extra (groupSort, groupOn)
 import Data.Maybe
 import Data.Ord
 import qualified Data.Map as M
@@ -63,10 +64,9 @@ nullacct = Account
 accountsFromPostings :: [Posting] -> [Account]
 accountsFromPostings ps =
   let
-    acctamts = [(paccount p,pamount p) | p <- ps]
-    grouped = groupBy (\a b -> fst a == fst b) $ sort $ acctamts
-    counted = [(a, length acctamts) | acctamts@((a,_):_) <- grouped]
-    summed = map (\as@((aname,_):_) -> (aname, sumStrict $ map snd as)) grouped -- always non-empty
+    grouped = groupSort [(paccount p,pamount p) | p <- ps]
+    counted = [(aname, length amts) | (aname, amts) <- grouped]
+    summed =  [(aname, sumStrict amts) | (aname, amts) <- grouped]  -- always non-empty
     nametree = treeFromPaths $ map (expandAccountName . fst) summed
     acctswithnames = nameTreeToAccount "root" nametree
     acctswithnumps = mapAccounts setnumps    acctswithnames where setnumps    a = a{anumpostings=fromMaybe 0 $ lookup (aname a) counted}
@@ -132,7 +132,7 @@ clipAccountsAndAggregate d as = combined
     where
       clipped  = [a{aname=clipOrEllipsifyAccountName d $ aname a} | a <- as]
       combined = [a{aebalance=sum (map aebalance same)}
-                  | same@(a:_) <- groupBy (\a1 a2 -> aname a1 == aname a2) clipped]
+                 | same@(a:_) <- groupOn aname clipped]
 {-
 test cases, assuming d=1:
 
diff --git a/hledger-lib/Hledger/Data/Journal.hs b/hledger-lib/Hledger/Data/Journal.hs
index 672b4e3c4..520ee942b 100644
--- a/hledger-lib/Hledger/Data/Journal.hs
+++ b/hledger-lib/Hledger/Data/Journal.hs
@@ -75,6 +75,7 @@ import Data.Array.ST
 import Data.Functor.Identity (Identity(..))
 import qualified Data.HashTable.ST.Cuckoo as HT
 import Data.List
+import Data.List.Extra (groupSort)
 -- import Data.Map (findWithDefault)
 import Data.Maybe
 import Data.Monoid
@@ -752,8 +753,7 @@ journalInferCommodityStyles j =
 commodityStylesFromAmounts :: [Amount] -> M.Map CommoditySymbol AmountStyle
 commodityStylesFromAmounts amts = M.fromList commstyles
   where
-    samecomm = \a1 a2 -> acommodity a1 == acommodity a2
-    commamts = [(acommodity $ head as, as) | as <- groupBy samecomm $ sortBy (comparing acommodity) amts]
+    commamts = groupSort [(acommodity as, as) | as <- amts]
     commstyles = [(c, canonicalStyleFrom $ map astyle as) | (c,as) <- commamts]
 
 -- | Given an ordered list of amount styles, choose a canonical style.