1 files changed, 32 insertions, 0 deletions

diff --git a/packages/special/lib/Numeric/GSL/Special.hs b/packages/special/lib/Numeric/GSL/Special.hs
index a8bbaf6..2994efb 100644
--- a/packages/special/lib/Numeric/GSL/Special.hs
+++ b/packages/special/lib/Numeric/GSL/Special.hs
@@ -15,6 +15,7 @@ Wrappers for selected special functions.
 -----------------------------------------------------------------------------
 
 module Numeric.GSL.Special (
+  -- * Functions
   module Numeric.GSL.Special.Airy
 , module Numeric.GSL.Special.Bessel
 , module Numeric.GSL.Special.Clausen
@@ -43,9 +44,12 @@ module Numeric.GSL.Special (
 , module Numeric.GSL.Special.Transport
 , module Numeric.GSL.Special.Trig
 , module Numeric.GSL.Special.Zeta
+-- * Util
+, mkComplex_e
 )
 where
 
+
 import Numeric.GSL.Special.Airy
 import Numeric.GSL.Special.Bessel
 import Numeric.GSL.Special.Clausen
@@ -74,3 +78,31 @@ import Numeric.GSL.Special.Synchrotron
 import Numeric.GSL.Special.Transport
 import Numeric.GSL.Special.Trig
 import Numeric.GSL.Special.Zeta
+
+import Data.Complex
+
+----------------------------------------------------------------
+
+{- | Some GSL complex functions work with separate real and imaginary parts stored in real variables, obtaining tuples (value, error) for the real and imaginary parts of the result:
+
+> > import Numeric.GSL.Special.Dilog
+
+> > complex_dilog_xy_e 1 1
+> ((0.6168502750680847,1.1097853812294034e-14),(1.4603621167531193,1.1855504863267322e-14))
+
+We can use @mkComplex_e@ to work with \"normal\" complex numbers:
+
+> > import Numeric.GSL.Special(mkComplex_e)
+> > import Data.Complex
+
+> > let dilogC = fst . mkComplex_e complex_dilog_xy_e
+
+> > dilogC (1 :+ 1)
+> 0.6168502750680847 :+ 1.4603621167531193
+
+-}
+mkComplex_e :: (Double -> Double -> ((Double, Double), (Double, Double)))
+            -> Complex Double -> (Complex Double, Complex Double)
+mkComplex_e f (x :+ y) = (zr :+ zi, er :+ ei)
+    where ((zr,er),(zi,ei)) = f x y
+