[commit: ghc] master: Weaken constraints on Data.Complex functions (7b04d35)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/7b04d35a87f1ee2904579a916ef1a6b0aa6fc7b8/ghc

>---------------------------------------------------------------

commit 7b04d35a87f1ee2904579a916ef1a6b0aa6fc7b8
Author: Herbert Valerio Riedel <hvr at gnu.org>
Date:   Sat Apr 19 13:56:36 2014 +0200

    Weaken constraints on Data.Complex functions
    
    The RealFloat data type context was dropped from Data.Complex some time
    ago (see ea280135dd888ac41d8804a9e37e358180cf13ac). However, the rest of
    the API in that module was left as-is even though many of the accessors
    in that module would work with much more general types now.
    
    This change simplifies the signatures of the functions above, which in
    the current API all unnecessarily take a RealFloat constraint that they
    don't use (and which may cause to pass around superflous type-class
    dictionaries):
    
        realPart  :: Complex a -> a
        imagPart  :: Complex a -> a
        conjugate :: Num a => Complex a -> Complex a
        mkPolar   :: Floating a => a -> a -> Complex a
        cis       :: Floating a => a -> Complex a
    
    This was originally proposed by Edward Kmett in
    
      http://www.haskell.org/pipermail/libraries/2014-March/022358.html
    
    Signed-off-by: Herbert Valerio Riedel <hvr at gnu.org>


>---------------------------------------------------------------

7b04d35a87f1ee2904579a916ef1a6b0aa6fc7b8
 libraries/base/Data/Complex.hs |   10 +++++-----
 libraries/base/changelog.md    |    2 ++
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/libraries/base/Data/Complex.hs b/libraries/base/Data/Complex.hs
index 190c598..b03848b 100644
--- a/libraries/base/Data/Complex.hs
+++ b/libraries/base/Data/Complex.hs
@@ -58,27 +58,27 @@ data Complex a
 -- Functions over Complex
 
 -- | Extracts the real part of a complex number.
-realPart :: (RealFloat a) => Complex a -> a
+realPart :: Complex a -> a
 realPart (x :+ _) =  x
 
 -- | Extracts the imaginary part of a complex number.
-imagPart :: (RealFloat a) => Complex a -> a
+imagPart :: Complex a -> a
 imagPart (_ :+ y) =  y
 
 -- | The conjugate of a complex number.
 {-# SPECIALISE conjugate :: Complex Double -> Complex Double #-}
-conjugate        :: (RealFloat a) => Complex a -> Complex a
+conjugate        :: Num a => Complex a -> Complex a
 conjugate (x:+y) =  x :+ (-y)
 
 -- | Form a complex number from polar components of magnitude and phase.
 {-# SPECIALISE mkPolar :: Double -> Double -> Complex Double #-}
-mkPolar          :: (RealFloat a) => a -> a -> Complex a
+mkPolar          :: Floating a => a -> a -> Complex a
 mkPolar r theta  =  r * cos theta :+ r * sin theta
 
 -- | @'cis' t@ is a complex value with magnitude @1@
 -- and phase @t@ (modulo @2*'pi'@).
 {-# SPECIALISE cis :: Double -> Complex Double #-}
-cis              :: (RealFloat a) => a -> Complex a
+cis              :: Floating a => a -> Complex a
 cis theta        =  cos theta :+ sin theta
 
 -- | The function 'polar' takes a complex number and
diff --git a/libraries/base/changelog.md b/libraries/base/changelog.md
index 3011fdf..a72e4e6 100644
--- a/libraries/base/changelog.md
+++ b/libraries/base/changelog.md
@@ -8,6 +8,8 @@
 
   * Add `Data.List.sortOn` sorting function
 
+  * Weaken RealFloat constraints on some `Data.Complex` functions
+
 ## 4.7.0.0  *Apr 2014*
 
   * Bundled with GHC 7.8.1