T.P.Shared: remove `backslashEscapes`, `escapeStringUsing`.

[API change]

These are inefficient association list lookups.
Replace with more efficient functions in the writers that
used them (with 10-25% performance improvements in
haddock, org, rtf, texinfo writers).

1 files changed, 13 insertions, 11 deletions

diff --git a/src/Text/Pandoc/Writers/Texinfo.hs b/src/Text/Pandoc/Writers/Texinfo.hs
index 0146fdfd8..6a33b4283 100644
--- a/src/Text/Pandoc/Writers/Texinfo.hs
+++ b/src/Text/Pandoc/Writers/Texinfo.hs
@@ -14,7 +14,7 @@ Conversion of 'Pandoc' format into Texinfo.
 module Text.Pandoc.Writers.Texinfo ( writeTexinfo ) where
 import Control.Monad.Except (throwError)
 import Control.Monad.State.Strict
-import Data.Char (chr, ord)
+import Data.Char (chr, ord, isAlphaNum)
 import Data.List (maximumBy, transpose, foldl')
 import Data.List.NonEmpty (nonEmpty)
 import Data.Ord (comparing)
@@ -85,16 +85,18 @@ pandocToTexinfo options (Pandoc meta blocks) = do
 
 -- | Escape things as needed for Texinfo.
 stringToTexinfo :: Text -> Text
-stringToTexinfo = escapeStringUsing texinfoEscapes
-  where texinfoEscapes = [ ('{', "@{")
-                         , ('}', "@}")
-                         , ('@', "@@")
-                         , ('\160', "@ ")
-                         , ('\x2014', "---")
-                         , ('\x2013', "--")
-                         , ('\x2026', "@dots{}")
-                         , ('\x2019', "'")
-                         ]
+stringToTexinfo t
+  | T.all isAlphaNum t = t
+  | otherwise = T.concatMap escChar t
+  where escChar '{'      = "@{"
+        escChar '}'      = "@}"
+        escChar '@'      = "@@"
+        escChar '\160'   = "@ "
+        escChar '\x2014' = "---"
+        escChar '\x2013' = "--"
+        escChar '\x2026' = "@dots{}"
+        escChar '\x2019' = "'"
+        escChar c        = T.singleton c
 
 escapeCommas :: PandocMonad m => TI m (Doc Text) -> TI m (Doc Text)
 escapeCommas parser = do