From 2c2bd8b27effd4ff011510bf49f02c06d56d3e98 Mon Sep 17 00:00:00 2001
From: Stephen Morgan <morgan.stephen99@gmail.com>
Date: Tue, 12 Jan 2021 13:52:59 +1100
Subject: [PATCH] lib: Refactor unlinesB to be cleaner and more efficient.

---
 hledger-lib/Hledger/Utils/Text.hs     | 16 +++++-----------
 hledger-lib/Text/Tabular/AsciiWide.hs |  2 +-
 2 files changed, 6 insertions(+), 12 deletions(-)

diff --git a/hledger-lib/Hledger/Utils/Text.hs b/hledger-lib/Hledger/Utils/Text.hs
index d81b932d4..4bb97ec35 100644
--- a/hledger-lib/Hledger/Utils/Text.hs
+++ b/hledger-lib/Hledger/Utils/Text.hs
@@ -66,19 +66,15 @@ module Hledger.Utils.Text
 where
 
 import Data.Char (digitToInt)
-import Data.List
+import Data.List (transpose)
 #if !(MIN_VERSION_base(4,11,0))
-import Data.Monoid
+import Data.Semigroup ((<>))
 #endif
 import Data.Text (Text)
 import qualified Data.Text as T
 import qualified Data.Text.Lazy.Builder as TB
--- import Text.Parsec
--- import Text.Printf (printf)
 
--- import Hledger.Utils.Parse
--- import Hledger.Utils.Regex
-import Hledger.Utils.Test
+import Hledger.Utils.Test ((@?=), test, tests)
 import Text.WideString (WideBuilder(..), wbToText, wbUnpack, charWidth, textWidth)
 
 
@@ -373,11 +369,9 @@ linesPrepend2 prefix1 prefix2 s = T.unlines $ case T.lines s of
     []   -> []
     l:ls -> (prefix1<>l) : map (prefix2<>) ls
 
--- | Concatenate a list of Text Builders with a newline between each item, and
--- another at the end. If the list is empty, return the identity builder.
+-- | Join a list of Text Builders with a newline after each item.
 unlinesB :: [TB.Builder] -> TB.Builder
-unlinesB [] = mempty
-unlinesB xs = mconcat (intersperse (TB.singleton '\n') xs) <> TB.singleton '\n'
+unlinesB = foldMap (<> TB.singleton '\n')
 
 -- | Read a decimal number from a Text. Assumes the input consists only of digit
 -- characters.
diff --git a/hledger-lib/Text/Tabular/AsciiWide.hs b/hledger-lib/Text/Tabular/AsciiWide.hs
index 18c144c35..0d71ac008 100644
--- a/hledger-lib/Text/Tabular/AsciiWide.hs
+++ b/hledger-lib/Text/Tabular/AsciiWide.hs
@@ -103,7 +103,7 @@ renderTableB topts@TableOpts{prettyTable=pretty, tableBorders=borders} fr fc f (
   -- borders and bars
   addBorders xs = if borders then bar VT SingleLine : xs ++ [bar VB SingleLine] else xs
   bar vpos prop = mconcat $ renderHLine vpos borders pretty sizes ch2 prop
-  unlinesB = (<>singleton '\n') . mconcat . intersperse "\n"
+  unlinesB = foldMap (<> singleton '\n')
 
 -- | Render a single row according to cell specifications.
 renderRow :: TableOpts -> Header Cell -> TL.Text