diff --git a/Numeric/Optimization/Algorithms/HagerZhang05.hsc b/Numeric/Optimization/Algorithms/HagerZhang05.hsc
--- a/Numeric/Optimization/Algorithms/HagerZhang05.hsc
+++ b/Numeric/Optimization/Algorithms/HagerZhang05.hsc
@@ -9,7 +9,7 @@
 --
 -- This module implements the algorithms described by Hager and
 -- Zhang [1].  We use bindings to @CG_DESCENT@ library by the same
--- authors, version 3.0 from 18/05/2008 [2].  The library code is
+-- authors, version 3.0 from 18\/05\/2008 [2].  The library code is
 -- also licensed under the terms of the GPL.
 --
 -- * [1] Hager, W. W. and Zhang, H.  /A new conjugate gradient/
@@ -30,6 +30,8 @@
     ,Function(..)
     ,Gradient(..)
     ,Combined(..)
+    ,PointMVector
+    ,GradientMVector
      -- ** Kinds of function types
     ,Simple
     ,Mutable
@@ -135,6 +137,15 @@
 -- | Phantom type for functions using mutable data.
 data Mutable
 
+-- | Mutable vector representing the point where the
+-- function\/gradient is begin evaluated.  This vector /should/
+-- /not/ be modified.
+type PointMVector m = SM.MVector (PrimState m) Double
+
+-- | Mutable vector representing where the gradient should be
+-- /written/.
+type GradientMVector m = SM.MVector (PrimState m) Double
+
 -- | Function calculating the value of the objective function @f@
 -- at a point @x@.
 data Function t where
@@ -142,7 +153,7 @@
               => (v Double -> Double)
               -> Function Simple
     MFunction :: (forall m. PrimMonad m
-                  => SM.MVector (PrimState m) Double
+                  => PointMVector m
                   -> m Double)
               -> Function Mutable
 
@@ -185,8 +196,8 @@
               => (v Double -> v Double)
               -> Gradient Simple
     MGradient :: (forall m. PrimMonad m
-                  => SM.MVector (PrimState m) Double
-                  -> SM.MVector (PrimState m) Double
+                  => PointMVector m
+                  -> GradientMVector m
                   -> m ())
               -> Gradient Mutable
 mutableG :: Gradient t -> Gradient Mutable
@@ -236,8 +247,8 @@
               => (v Double -> (Double, v Double))
               -> Combined Simple
     MCombined :: (forall m. PrimMonad m
-                  => SM.MVector (PrimState m) Double
-                  -> SM.MVector (PrimState m) Double
+                  => PointMVector m
+                  -> GradientMVector m
                   -> m Double)
               -> Combined Mutable
 mutableC :: Combined t -> Combined Mutable
diff --git a/nonlinear-optimization.cabal b/nonlinear-optimization.cabal
--- a/nonlinear-optimization.cabal
+++ b/nonlinear-optimization.cabal
@@ -3,7 +3,7 @@
 Tested-With:         GHC
 Category:            Math
 Name:                nonlinear-optimization
-Version:             0.2
+Version:             0.3
 Stability:           experimental
 License:             GPL
 License-File:        LICENSE