diff --git a/changelog b/changelog
--- a/changelog
+++ b/changelog
@@ -1,3 +1,11 @@
+texmath (0.9.1)
+
+  * Pandoc writer:  add thin space after math operators.
+  * TeX reader: improve parsing of `\mathop` to allow
+    multi-character operator names.
+  * Minor optimizations.
+  * Added Ord instances to Exp and associated types.
+
 texmath (0.9)
 
   * OMML writer: Properly handle nary inside delimiters (#92).
diff --git a/src/Text/TeXMath/Readers/TeX.hs b/src/Text/TeXMath/Readers/TeX.hs
--- a/src/Text/TeXMath/Readers/TeX.hs
+++ b/src/Text/TeXMath/Readers/TeX.hs
@@ -143,6 +143,7 @@
 operatorname :: TP (Exp, Bool)
 operatorname = do
     ctrlseq "operatorname"
+    -- these are slightly different but we won't worry about that here...
     convertible <- (char '*' >> spaces >> return True) <|> return False
     op <- expToOperatorName <$> texToken
     maybe mzero (\s -> return (EMathOperator s, convertible)) op
@@ -187,10 +188,11 @@
   <|> return Nothing
 
 binomCmd :: TP String
-binomCmd = oneOfCommands (map fst binomCmds)
+binomCmd = oneOfCommands (M.keys binomCmds)
 
-binomCmds :: [(String, Exp -> Exp -> Exp)]
-binomCmds = [ ("\\choose", \x y ->
+binomCmds :: M.Map String (Exp -> Exp -> Exp)
+binomCmds = M.fromList
+            [ ("\\choose", \x y ->
                 EDelimited "(" ")" [Right (EFraction NoLineFrac x y)])
             , ("\\brack", \x y ->
                 EDelimited "[" "]" [Right (EFraction NoLineFrac x y)])
@@ -233,7 +235,7 @@
                 else many (notFollowedBy binomCmd >> p)
   let withCmd :: String -> TP Exp
       withCmd cmd =
-         case lookup cmd binomCmds of
+         case M.lookup cmd binomCmds of
               Just f  -> f <$> (asGroup <$> pure initial)
                            <*> (asGroup <$> many p)
               Nothing -> fail $ "Unknown command " ++ cmd
@@ -622,7 +624,10 @@
   case e of
      ESymbol _ x   -> return $ ESymbol ty x
      EIdentifier x -> return $ ESymbol ty x
-     x             -> return x
+     x | ty == Op  -> case expToOperatorName x of
+                           Just y -> return $ EMathOperator y
+                           _      -> return x
+       | otherwise -> return x
 
 binary :: TP Exp
 binary = do
diff --git a/src/Text/TeXMath/Shared.hs b/src/Text/TeXMath/Shared.hs
--- a/src/Text/TeXMath/Shared.hs
+++ b/src/Text/TeXMath/Shared.hs
@@ -39,6 +39,7 @@
 import Text.TeXMath.Types
 import Text.TeXMath.TeX
 import qualified Data.Map as M
+import qualified Data.Set as Set
 import Data.Maybe (fromMaybe)
 import Data.Ratio ((%))
 import Data.List (sort)
@@ -83,7 +84,7 @@
                   (snd <$> M.lookup t textTypesMap) in
   if textPackage textCmd e
     then textCmd
-    else fromMaybe "\\mathrm" (lookup textCmd alts)
+    else fromMaybe "\\mathrm" (M.lookup textCmd alts)
 
 -- | Maps MathML mathvariant to the corresponing TextType
 getTextType :: String -> TextType
@@ -127,10 +128,10 @@
 -- Operator Table
 
 getOperator :: Exp -> Maybe TeX
-getOperator op = fmap ControlSeq $ lookup op operators
+getOperator op = fmap ControlSeq $ M.lookup op operators
 
-operators :: [(Exp, String)]
-operators =
+operators :: M.Map Exp String
+operators = M.fromList
            [ (EMathOperator "arccos", "\\arccos")
            , (EMathOperator "arcsin", "\\arcsin")
            , (EMathOperator "arctan", "\\arctan")
@@ -212,18 +213,28 @@
   , ( TextBoldFraktur         , ("bold-fraktur","\\mathbffrak"))
   , ( TextSansSerifItalic     , ("sans-serif-italic","\\mathsfit")) ]
 
-unicodeMath, base :: [String]
-unicodeMath = ["\\mathbfit", "\\mathbfsfup", "\\mathbfsfit", "\\mathbfscr", "\\mathbffrak", "\\mathsfit"]
-base = ["\\mathbb", "\\mathrm", "\\mathbf", "\\mathit", "\\mathsf", "\\mathtt", "\\mathfrak", "\\mathcal"]
+unicodeMath, base :: Set.Set String
+unicodeMath = Set.fromList
+  ["\\mathbfit", "\\mathbfsfup", "\\mathbfsfit", "\\mathbfscr",
+   "\\mathbffrak", "\\mathsfit"]
+base = Set.fromList
+  ["\\mathbb", "\\mathrm", "\\mathbf", "\\mathit", "\\mathsf",
+   "\\mathtt", "\\mathfrak", "\\mathcal"]
 
-alts :: [(String, String)]
-alts = [ ("\\mathbfit", "\\mathbf"), ("\\mathbfsfup", "\\mathbf"), ("\\mathbfsfit", "\\mathbf")
-       , ("\\mathbfscr", "\\mathcal"), ("\\mathbffrak", "\\mathfrak"), ("\\mathsfit", "\\mathsf")]
+alts :: M.Map String String
+alts = M.fromList
+  [ ("\\mathbfit", "\\mathbf")
+  , ("\\mathbfsfup", "\\mathbf")
+  , ("\\mathbfsfit", "\\mathbf")
+  , ("\\mathbfscr", "\\mathcal")
+  , ("\\mathbffrak", "\\mathfrak")
+  , ("\\mathsfit", "\\mathsf")
+  ]
 
 textPackage :: String -> [String] -> Bool
 textPackage s e
-  | s `elem` unicodeMath = "unicode-math" `elem` e
-  | s `elem` base    = True
+  | s `Set.member` unicodeMath = "unicode-math" `elem` e
+  | s `Set.member` base    = True
   | otherwise = True
 
 -- | Mapping between LaTeX scaling commands and the scaling factor
@@ -325,10 +336,9 @@
 
 -- Converts unit to multiplier to reach em
 unitToMultiplier :: String -> Maybe Rational
-unitToMultiplier s = lookup s units
+unitToMultiplier s = M.lookup s units
   where
-    units =
-                        [ ( "pt" , 10)
+    units = M.fromList  [ ( "pt" , 10)
                         , ( "mm" , (351/10))
                         , ( "cm" , (35/100))
                         , ( "in" , (14/100))
diff --git a/src/Text/TeXMath/Types.hs b/src/Text/TeXMath/Types.hs
--- a/src/Text/TeXMath/Types.hs
+++ b/src/Text/TeXMath/Types.hs
@@ -32,16 +32,16 @@
 
 data TeXSymbolType = Ord | Op | Bin | Rel | Open | Close | Pun | Accent
                      | Fence | TOver | TUnder | Alpha | BotAccent | Rad
-                     deriving (Show, Read, Eq, Data, Typeable)
+                     deriving (Show, Read, Eq, Ord, Data, Typeable)
 
 data Alignment = AlignLeft | AlignCenter | AlignRight | AlignDefault
-                 deriving (Show, Read, Eq, Data, Typeable)
+                 deriving (Show, Read, Eq, Ord, Data, Typeable)
 
 data FractionType = NormalFrac   -- ^ Displayed or textual, acc to 'DisplayType'
                   | DisplayFrac  -- ^ Force display mode
                   | InlineFrac   -- ^ Force inline mode (textual)
                   | NoLineFrac   -- ^ No line between top and bottom
-                  deriving (Show, Read, Eq, Data, Typeable)
+                  deriving (Show, Read, Eq, Ord, Data, Typeable)
 
 type ArrayLine = [[Exp]]
 
@@ -90,7 +90,7 @@
                   -- the same length.
   | EText TextType String  -- ^ Some normal text, possibly styled.
   | EStyled TextType [Exp] -- ^  A group of styled expressions.
-  deriving (Show, Read, Eq, Data, Typeable)
+  deriving (Show, Read, Eq, Ord, Data, Typeable)
 
 -- | An @EDelimited@ element contains a string of ordinary expressions
 -- (represented here as @Right@ values) or fences (represented here as
@@ -100,7 +100,7 @@
 
 data DisplayType = DisplayBlock  -- ^ A displayed formula.
                  | DisplayInline  -- ^ A formula rendered inline in text.
-                 deriving (Show, Eq)
+                 deriving (Show, Eq, Ord)
 
 data TextType = TextNormal
               | TextBold
@@ -116,7 +116,7 @@
               | TextBoldScript
               | TextBoldFraktur
               | TextSansSerifItalic
-              deriving (Show, Ord, Read, Eq, Data, Typeable)
+              deriving (Show, Read, Eq, Ord, Data, Typeable)
 
 data FormType = FPrefix | FPostfix | FInfix deriving (Show, Ord, Eq)
 
diff --git a/src/Text/TeXMath/Unicode/Fonts.hs b/src/Text/TeXMath/Unicode/Fonts.hs
--- a/src/Text/TeXMath/Unicode/Fonts.hs
+++ b/src/Text/TeXMath/Unicode/Fonts.hs
@@ -28,7 +28,7 @@
 Utilities to convert between MS font codepoints and unicode characters.
 -}
 module Text.TeXMath.Unicode.Fonts (getUnicode, Font(..), stringToFont) where
-
+import qualified Data.Map as M
 
 -- | Enumeration of recognised fonts
 data Font = Symbol -- ^ <http://en.wikipedia.org/wiki/Symbol_(typeface) Adobe Symbol>
@@ -42,11 +42,11 @@
 -- | Given a font and codepoint, returns the corresponding unicode
 -- character
 getUnicode :: Font -> Char -> Maybe Char
-getUnicode Symbol c = lookup c symbol
+getUnicode Symbol c = M.lookup c symbol
 
 -- Generated from lib/fonts/symbol.txt
-symbol :: [(Char, Char)]
-symbol =
+symbol :: M.Map Char Char
+symbol = M.fromList
   [ (' ',' ')
   , (' ','\160')
   , ('!','!')
diff --git a/src/Text/TeXMath/Writers/Pandoc.hs b/src/Text/TeXMath/Writers/Pandoc.hs
--- a/src/Text/TeXMath/Writers/Pandoc.hs
+++ b/src/Text/TeXMath/Writers/Pandoc.hs
@@ -47,6 +47,8 @@
 addSpaces (x : ESymbol t2 s2 : xs)
   | not (null xs) =
     x : addSpace t2 (ESymbol t2 s2) ++ addSpaces xs
+addSpaces (EMathOperator s : xs) =
+  EMathOperator s : thinspace : addSpaces xs
 addSpaces (x : xs) = x : addSpaces xs
 addSpaces [] = []
 
@@ -57,9 +59,11 @@
       Rel -> [widespace, x, widespace]
       Pun -> [x, thinspace]
       _   -> [x]
-  where thinspace = EText TextNormal "\x2006"
-        medspace  = EText TextNormal "\x2005"
-        widespace = EText TextNormal "\x2004"
+
+thinspace, medspace, widespace :: Exp
+thinspace = EText TextNormal "\x2006"
+medspace  = EText TextNormal "\x2005"
+widespace = EText TextNormal "\x2004"
 
 renderStr :: TextType -> String -> Inline
 renderStr tt s =
diff --git a/texmath.cabal b/texmath.cabal
--- a/texmath.cabal
+++ b/texmath.cabal
@@ -1,5 +1,5 @@
 Name:                texmath
-Version:             0.9
+Version:             0.9.1
 Cabal-Version:       >= 1.10
 Build-type:          Simple
 Synopsis:            Conversion between formats used to represent mathematics.