fixed bugs where the negate function wasn't treated as a math expr an…

…d improved the pretty printer when negates are displayed

README.md

@@ -30,11 +30,11 @@ If you compile the linear package with Herbie, the code above gets rewritten to:
 
 ```
 w :: Double -> Double -> Double
-w far near = if far < (negate 1.7210442634149447e81)
-    then (far / (far - near)) * 2 * near
+w far near = if far < -1.7210442634149447e81
+    then ((-2 * far) / (far - near)) * near
     else if far < 8.364504563556443e16
-        then (far * 2) / ((far - near) / near)
-        else (far / (far - near)) * 2 * near
+        then -2 * far * (near / (far - near))
+        else ((-2 * far) / (far - near)) * near
 ```
 
 This modified code is numerically stable.

src/Herbie/MathExpr.hs

@@ -31,6 +31,7 @@ monOpList =
     , "sqrt"
     , "abs"
     , "size"
+    , "negate"
     ]
 
 binOpList = [ "^", "**", "^^", "/", "-", "expt" ] ++ commutativeOpList
@@ -180,6 +181,7 @@ mathExpr2lisp :: MathExpr -> String
 mathExpr2lisp = go
     where
         go (EBinOp op a1 a2) = "("++op++" "++go a1++" "++go a2++")"
+        go (EMonOp "negate" a) = "(- "++go a++")"
         go (EMonOp op a) = "("++op++" "++go a++")"
         go (EIf cond e1 e2) = "(if "++go cond++" "++go e1++" "++go e2++")"
         go (ELeaf e) = e

src/Herbie/MathInfo.hs

@@ -74,16 +74,20 @@ pprMathInfo mathInfo = go 1 False $ getMathExpr mathInfo
             else str
             where
                 str = case e of
-                    EMonOp op e1 -> op++" "++ go i True e1
+--                     EMonOp "negate" l@(ELit _) -> "-"++go i False l
+                    EMonOp "negate" e1 ->     "-"++go i False e1
+                    EMonOp op       e1 -> op++" "++go i True  e1
 
                     EBinOp op e1 e2 -> go i parens1 e1++" "++op++" "++go i parens2 e2
                         where
                             parens1 = case e1 of
                                 (EBinOp op' _ _) -> op/=op'
+                                (EMonOp _ _) -> False
                                 _ -> True
 
                             parens2 = case e2 of
                                 (EBinOp op' _ _) -> op/=op' || not (op `elem` commutativeOpList)
+                                (EMonOp _ _) -> False
                                 _ -> True
 
                     ELit l -> if toRational (floor l) == l

test/Tests.hs

@@ -13,7 +13,6 @@ module Main
 
 import SubHask
 
-{-
 --------------------------------------------------------------------------------
 
 -- This section tests that Herbie obeys the code annotations
@@ -295,9 +294,6 @@ example87 x = exp x / sqrt(exp x - 1) * sqrt x
 example88 x = (exp(x) - 1) / x
 
 example89 x = sqrt(x + 2) - sqrt(x)
--}
-
---------------------------------------------------------------------------------
 
 --------------------------------------------------------------------------------
 

test/ValidRewrite.hs

@@ -1,5 +1,6 @@
 {-# LANGUAGE GADTs,RebindableSyntax,CPP,FlexibleContexts,FlexibleInstances,ConstraintKinds #-}
 {-# LANGUAGE StandaloneDeriving,DeriveDataTypeable #-}
+{-# OPTIONS_GHC -dcore-lint #-}
 {-
  - This test suite ensures that the rewrites that HerbiePlugin performs
  - give the correct results.
@@ -27,11 +28,11 @@ test1b far near = -(2 * far * near) / (far - near)
 
 {-# ANN test1c "NoHerbie" #-}
 test1c :: Double -> Double -> Double
-test1c far near = -(if far < (negate 1.7210442634149447e81)
-    then (far / (far - near)) * 2 * near
+test1c far near = if far < -1.7210442634149447e81
+    then ((-2 * far) / (far - near)) * near
     else if far < 8.364504563556443e16
-        then (far * 2) / ((far - near) / near)
-        else (far / (far - near)) * 2 * near)
+        then -2 * far * (near / (far - near))
+        else ((-2 * far) / (far - near)) * near
 
 --------------------
 
@@ -85,16 +86,16 @@ atanh_ x = 0.5 * log ((1.0+x) / (1.0-x))
     putStrLn ""
 
 main = do
---     mkTest(test1a,test1b,-2e90,6)
---     mkTest(test1a,test1b,3,4)
---     mkTest(test1a,test1b,2e90,6)
---
---     mkTest(test1a,test1c,-2e90,6)
---     mkTest(test1a,test1c,3,4)
---     mkTest(test1a,test1c,2e90,6)
---
---     mkTest(test2a,test2b,1,2)
---
+    mkTest(test1a,test1b,-2e90,6)
+    mkTest(test1a,test1b,3,4)
+    mkTest(test1a,test1b,2e90,6)
+
+    mkTest(test1a,test1c,-2e90,6)
+    mkTest(test1a,test1c,3,4)
+    mkTest(test1a,test1c,2e90,6)
+
+    mkTest(test2a,test2b,1,2)
+
 --     mkTest(test3a,test3b,(Quaternion 1 (V3 1 2 3)),(Quaternion 2 (V3 2 3 4)))
 
 --     mkTestB(asinh,asinh_,5e-17::Complex Double)