Add benchmarks for gh-165

I used the code from the gist as the source for the Concat module.

benchmarks/haskell/Benchmarks.hs

@@ -10,6 +10,7 @@ import System.FilePath ((</>))
 import System.IO (IOMode (WriteMode), openFile, hSetEncoding, utf8)
 
 import qualified Benchmarks.Builder as Builder
+import qualified Benchmarks.Concat as Concat
 import qualified Benchmarks.DecodeUtf8 as DecodeUtf8
 import qualified Benchmarks.EncodeUtf8 as EncodeUtf8
 import qualified Benchmarks.Equality as Equality
@@ -41,6 +42,7 @@ benchmarks = do
     -- Traditional benchmarks
     bs <- sequence
         [ Builder.benchmark
+        , Concat.benchmark
         , DecodeUtf8.benchmark "html" (tf "libya-chinese.html")
         , DecodeUtf8.benchmark "xml" (tf "yiwiki.xml")
         , DecodeUtf8.benchmark "ascii" (tf "ascii.txt")

benchmarks/haskell/Benchmarks/Concat.hs

+{-# LANGUAGE OverloadedStrings #-}
+
+module Benchmarks.Concat (benchmark) where
+
+import Control.Monad.Trans.Writer
+import Criterion (Benchmark, bgroup, bench, whnf)
+import Data.Text as T
+
+benchmark :: IO Benchmark
+benchmark = return $ bgroup "Concat"
+  [ bench "append" $ whnf (append4 "Text 1" "Text 2" "Text 3") "Text 4"
+  , bench "concat" $ whnf (concat4 "Text 1" "Text 2" "Text 3") "Text 4"
+  , bench "write"  $ whnf (write4  "Text 1" "Text 2" "Text 3") "Text 4"
+  ]
+
+append4, concat4, write4 :: Text -> Text -> Text -> Text -> Text
+
+{-# NOINLINE append4 #-}
+append4 x1 x2 x3 x4 = x1 `append` x2 `append` x3 `append` x4
+
+{-# NOINLINE concat4 #-}
+concat4 x1 x2 x3 x4 = T.concat [x1, x2, x3, x4]
+
+{-# NOINLINE write4 #-}
+write4 x1 x2 x3 x4 = execWriter $ tell x1 >> tell x2 >> tell x3 >> tell x4

benchmarks/text-benchmarks.cabal

@@ -47,6 +47,7 @@ executable text-benchmarks
                   ghc-prim,
                   integer-gmp,
                   stringsearch,
+                  transformers,
                   utf8-string,
                   vector