diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -145,7 +145,7 @@
 For more examples, see the [eg](eg) and [bench](bench) folders.
 
 Speculate has been subject to a paper, see the
-[(Draft) Paper about Speculate (to appear) on Haskell Symposium 2017](https://matela.com.br/paper/speculate.pdf).
+[Speculate Paper on Haskell Symposium 2017](https://matela.com.br/paper/speculate.pdf).
 
 [leancheck]: https://hackage.haskell.org/package/leancheck
 [LeanCheck]: https://hackage.haskell.org/package/leancheck
diff --git a/speculate.cabal b/speculate.cabal
--- a/speculate.cabal
+++ b/speculate.cabal
@@ -1,5 +1,5 @@
 name:                speculate
-version:             0.2.5
+version:             0.2.6
 synopsis:            discovery of properties about Haskell functions
 description:
   Speculate automatically discovers laws about Haskell functions.
@@ -31,7 +31,7 @@
 source-repository this
   type:            git
   location:        https://github.com/rudymatela/speculate
-  tag:             v0.2.5
+  tag:             v0.2.6
 
 
 library
diff --git a/src/Test/Speculate/Expr/Core.hs b/src/Test/Speculate/Expr/Core.hs
--- a/src/Test/Speculate/Expr/Core.hs
+++ b/src/Test/Speculate/Expr/Core.hs
@@ -142,7 +142,8 @@
                     hs -> "  (holes: " ++ intercalate ", " (map show hs) ++ ")"
 
 showsPrecExpr :: Int -> Expr -> String -> String
-showsPrecExpr d (Constant s _) | atomic s && isInfixedPrefix s = showString $ toPrefix s
+showsPrecExpr d (Constant s _) | isInfixedPrefix s = showString $ toPrefix s
+showsPrecExpr d (Constant s _) | isNegativeLiteral s = showParen (d > 0) $ showString s
 showsPrecExpr d (Constant s _) = showParen sp $ showString s
   where sp = if atomic s then isInfix s else maybe True (d >) $ outernmostPrec s
 showsPrecExpr d (Var "" _)     = showString "_" -- a hole
diff --git a/src/Test/Speculate/Utils/String.hs b/src/Test/Speculate/Utils/String.hs
--- a/src/Test/Speculate/Utils/String.hs
+++ b/src/Test/Speculate/Utils/String.hs
@@ -13,6 +13,7 @@
   , unquote
   , atomic
   , outernmostPrec
+  , isNegativeLiteral
   , isInfix, isPrefix, isInfixedPrefix
   , toPrefix
   , prec
@@ -46,6 +47,12 @@
     [l,o,r] | isInfix o -> Just (prec o)
     _                   -> Nothing
 
+isNegativeLiteral :: String -> Bool
+isNegativeLiteral s | not (atomic s) = False
+isNegativeLiteral "-"                = False
+isNegativeLiteral ('-':cs)           = all isDigit cs
+isNegativeLiteral _                  = False
+
 -- | Check if a function / operator is infix
 --
 -- > isInfix "foo"   == False
@@ -95,8 +102,9 @@
 
 -- | Is the string of the form @`string`@
 isInfixedPrefix :: String -> Bool
-isInfixedPrefix ('`':cs) = last cs == '`'
-isInfixedPrefix _ = False
+isInfixedPrefix s | not (atomic s) = False
+isInfixedPrefix ('`':cs)           = last cs == '`'
+isInfixedPrefix _                  = False
 
 -- | Transform an infix operator into an infix function:
 --
diff --git a/tests/Test.hs b/tests/Test.hs
--- a/tests/Test.hs
+++ b/tests/Test.hs
@@ -42,15 +42,16 @@
   --   Operators are surrounded by dashes.
 
   -- ** Integers
-  , zero, one
+  , zero, one, two, minusOne, minusTwo
   , xx, yy, zz, xx'
   , id', abs'
-  , (-+-), (-*-), (.-.)
+  , (-+-), (-*-), (.-.), (-.-)
   , ii, jj, kk, ii'
   , negate'
   , ff, gg
   , ff2, hh2, hh3, hh4, hh5, hh6, hh7
   , succ'
+  , (-$-)
 
   , idE
   , absE
@@ -59,6 +60,9 @@
   , plusE
   , timesE
   , minusE
+  , commaE
+  , ffE
+  , ggE
 
   -- ** Booleans
   , true, false
@@ -281,6 +285,15 @@
 one :: Expr
 one = showConstant (1 :: Int)
 
+two :: Expr
+two = showConstant (2 :: Int)
+
+minusOne :: Expr
+minusOne = showConstant (-1 :: Int)
+
+minusTwo :: Expr
+minusTwo = showConstant (-2 :: Int)
+
 xx :: Expr -- ex
 xx = var "x" int
 
@@ -336,6 +349,19 @@
 minusE :: Expr
 minusE = constant "-" ((-) :: Int -> Int -> Int)
 
+(-.-) :: Expr -> Expr -> Expr
+e1 -.- e2 = commaE :$ e1 :$ e2
+
+commaE :: Expr
+commaE = constant "," ((,) :: Int -> Int -> (Int,Int))
+
+(-$-) :: Expr -> Expr -> Expr
+e1 -$- e2 = applyE :$ e1 :$ e2
+infixl 6 -$-
+
+applyE :: Expr
+applyE = constant "$" (($) :: (Int -> Int) -> Int -> Int)
+
 ii :: Expr
 ii = var "i" int
 
@@ -349,10 +375,16 @@
 ii' = var "i'" int
 
 ff :: Expr -> Expr
-ff = (ffE :$) where ffE = constant "f" (undefined :: Int -> Int)
+ff = (ffE :$)
 
+ffE :: Expr
+ffE = constant "f" (undefined :: Int -> Int)
+
 gg :: Expr -> Expr
-gg = (ggE :$) where ggE = constant "g" (undefined :: Int -> Int)
+gg = (ggE :$)
+
+ggE :: Expr
+ggE = constant "g" (undefined :: Int -> Int)
 
 ff2 :: Expr -> Expr -> Expr
 ff2 e1 e2 = ffE :$ e1 :$ e2
diff --git a/tests/test-expr.hs b/tests/test-expr.hs
--- a/tests/test-expr.hs
+++ b/tests/test-expr.hs
@@ -204,4 +204,23 @@
   , show (cc -:- space -:- dd -:- lineBreak -:- ccs)         == "c:' ':d:'\\n':cs :: [Char]"
   , show (cc -:- aa -:- bb -:- emptyString) == "c:\"ab\" :: [Char]"
   , show (cc -:- aa -:- bb -:- space -:- aa -:- bb -:- emptyString) == "c:\"ab ab\" :: [Char]"
+
+  , show one                     == "1 :: Int"
+  , show (minusOne)              == "-1 :: Int"
+  , show (one -+- one)           == "1 + 1 :: Int"
+  , show (minusOne -+- minusOne) == "(-1) + (-1) :: Int"
+
+  , show (zero -.- one)          == "(0,1) :: (Int,Int)"
+  , show (minusOne -.- minusOne) == "(-1,-1) :: (Int,Int)"
+
+  , show (one -:- ll)                     == "[1] :: [Int]"
+  , show (zero -:- one -:- ll)            == "[0,1] :: [Int]"
+  , show (minusOne -:- ll)                == "[-1] :: [Int]"
+  , show (minusOne -:- minusTwo -:- ll)   == "[-1,-2] :: [Int]"
+  , show (xx -:- minusTwo -:- yy -:- ll)  == "[x,-2,y] :: [Int]"
+  , show (xx -:- minusTwo -:- yy -:- xxs) == "x:(-2):y:xs :: [Int]"
+
+  , show (ffE -$- zero)     == "f $ 0 :: Int"
+  , show (ggE -$- xx)       == "g $ x :: Int"
+  , show (ffE -$- minusOne) == "f $ (-1) :: Int"
   ]