diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -5,6 +5,13 @@
 ## Unreleased changes
 
 
+## 0.6.2.0
+
+-   Improve leapfrog integrator.
+-   Update tooling.
+-   Cleanup proposals.
+
+
 ## 0.6.1.0
 
 -   Revamp Hamiltonian proposal (storable vectors).
@@ -70,7 +77,7 @@
 ## 0.2.4
 
 -   **Change order of arguments for proposals**.
--   'slideStem' was renamed to 'slideBranch'.
+-   ’slideStem’ was renamed to ’slideBranch’.
 -   Change ProposalSimple from newtype to type.
 -   Contravariant instances of parameter and batch monitors. Use `(>$<)` instead
     of `(@.)` and `(@#)`.
diff --git a/mcmc.cabal b/mcmc.cabal
--- a/mcmc.cabal
+++ b/mcmc.cabal
@@ -1,6 +1,6 @@
-cabal-version:  2.2
+cabal-version:  3.0
 name:           mcmc
-version:        0.6.1.0
+version:        0.6.2.0
 synopsis:       Sample from a posterior using Markov chain Monte Carlo
 description:    Please see the README on GitHub at <https://github.com/dschrempf/mcmc#readme>
 category:       Math, Statistics
@@ -116,7 +116,6 @@
   build-depends:
       base >=4.7 && <5
     , hspec
-    , log-domain
     , mcmc
     , mwc-random
     , statistics
diff --git a/src/Mcmc/Algorithm/MC3.hs b/src/Mcmc/Algorithm/MC3.hs
--- a/src/Mcmc/Algorithm/MC3.hs
+++ b/src/Mcmc/Algorithm/MC3.hs
@@ -255,11 +255,11 @@
   -- Only set the id for the cold chain.
   | i == 0 = return $ MHG $ c {chainId = Just 0}
   | otherwise = do
-    -- We have to push the current link in the trace, since it is not set by
-    -- 'setReciprocalTemperature'. The other links in the trace are still
-    -- pointing to the link of the cold chain, but this has no effect.
-    t' <- pushT l t
-    return $ MHG $ c {chainId = Just i, trace = t'}
+      -- We have to push the current link in the trace, since it is not set by
+      -- 'setReciprocalTemperature'. The other links in the trace are still
+      -- pointing to the link of the cold chain, but this has no effect.
+      t' <- pushT l t
+      return $ MHG $ c {chainId = Just i, trace = t'}
   where
     a' = setReciprocalTemperature prf lhf beta a
     c = fromMHG a'
@@ -291,11 +291,11 @@
   | sp < 1 = error "mc3: The swap period must be strictly positive."
   | sn < 1 || sn > n - 1 = error "mc3: The number of swaps must be in [1, NChains - 1]."
   | otherwise = do
-    -- Split random number generators.
-    gs <- V.fromList <$> splitGen n g
-    cs <- V.mapM (mhg s pr lh cc mn i0) gs
-    hcs <- V.izipWithM (initMHG pr lh) (V.convert bs) cs
-    return $ MC3 sMc3 hcs bs 0 (emptyA [0 .. n - 2]) g
+      -- Split random number generators.
+      gs <- V.fromList <$> splitGen n g
+      cs <- V.mapM (mhg s pr lh cc mn i0) gs
+      hcs <- V.izipWithM (initMHG pr lh) (V.convert bs) cs
+      return $ MC3 sMc3 hcs bs 0 (emptyA [0 .. n - 2]) g
   where
     n = fromNChains $ mc3NChains sMc3
     sp = fromSwapPeriod $ mc3SwapPeriod sMc3
diff --git a/src/Mcmc/Algorithm/MHG.hs b/src/Mcmc/Algorithm/MHG.hs
--- a/src/Mcmc/Algorithm/MHG.hs
+++ b/src/Mcmc/Algorithm/MHG.hs
@@ -170,8 +170,8 @@
 mhgAccept r g
   | ln r >= 0.0 = return True
   | otherwise = do
-    b <- uniform g
-    return $ b < exp (ln r)
+      b <- uniform g
+      return $ b < exp (ln r)
 
 mhgPropose :: MHG a -> Proposal a -> IO (MHG a)
 mhgPropose (MHG c) p = do
diff --git a/src/Mcmc/Chain/Save.hs b/src/Mcmc/Chain/Save.hs
--- a/src/Mcmc/Chain/Save.hs
+++ b/src/Mcmc/Chain/Save.hs
@@ -91,19 +91,19 @@
   IO (Chain a)
 fromSavedChain pr lh cc mn (SavedChain ci it i tr ac' g' ts)
   | pr (state it) /= prior it =
-    let msg =
-          unlines
-            [ "fromSave: Provided prior function does not match the saved prior.",
-              "fromSave: Current prior:" <> show (prior it) <> ".",
-              "fromSave: Given prior:" <> show (pr $ state it) <> "."
-            ]
-     in error msg
+      let msg =
+            unlines
+              [ "fromSave: Provided prior function does not match the saved prior.",
+                "fromSave: Current prior:" <> show (prior it) <> ".",
+                "fromSave: Given prior:" <> show (pr $ state it) <> "."
+              ]
+       in error msg
   | lh (state it) /= likelihood it =
-    error "fromSave: Provided likelihood function does not match the saved likelihood."
+      error "fromSave: Provided likelihood function does not match the saved likelihood."
   | otherwise = do
-    g <- loadGen g'
-    tr' <- thawT tr
-    return $ Chain ci it i tr' ac g i pr lh cc' mn
+      g <- loadGen g'
+      tr' <- thawT tr
+      return $ Chain ci it i tr' ac g i pr lh cc' mn
   where
     ac = transformKeysA [0 ..] (ccProposals cc) ac'
     tunePs mt p = case mt of
diff --git a/src/Mcmc/Cycle.hs b/src/Mcmc/Cycle.hs
--- a/src/Mcmc/Cycle.hs
+++ b/src/Mcmc/Cycle.hs
@@ -138,6 +138,15 @@
   where
     once = sum $ map (fromPWeight . prWeight) xs
 
+-- See 'tuneWithTuningParameters' and 'Tuner'.
+tuneWithChainParameters :: AcceptanceRate -> VB.Vector a -> Proposal a -> Either String (Proposal a)
+tuneWithChainParameters ar xs p = case prTuner p of
+  Nothing -> Left "tuneWithChainParameters: Proposal is not tunable."
+  Just (Tuner t fT ts fTs _) ->
+    let t' = fT ar t
+        ts' = fTs xs ts
+     in tuneWithTuningParameters t' ts' p
+
 -- | Calculate acceptance rates and auto tunes the 'Proposal's in the 'Cycle'.
 --
 -- Do not change 'Proposal's that are not tuneable.
diff --git a/src/Mcmc/Internal/Gamma.hs b/src/Mcmc/Internal/Gamma.hs
--- a/src/Mcmc/Internal/Gamma.hs
+++ b/src/Mcmc/Internal/Gamma.hs
@@ -77,8 +77,8 @@
 lgamma15_2 :: RealFloat a => a -> a -> a
 lgamma15_2 zm1 zm2 =
   r * y + r
-    * ( evaluatePolynomial (- zm2) tableLogGamma_15_2P
-          / evaluatePolynomial (- zm2) tableLogGamma_15_2Q
+    * ( evaluatePolynomial (-zm2) tableLogGamma_15_2P
+          / evaluatePolynomial (-zm2) tableLogGamma_15_2Q
       )
   where
     r = zm1 * zm2
diff --git a/src/Mcmc/Internal/Random.hs b/src/Mcmc/Internal/Random.hs
--- a/src/Mcmc/Internal/Random.hs
+++ b/src/Mcmc/Internal/Random.hs
@@ -33,8 +33,8 @@
 splitGen n gen
   | n <= 0 = return []
   | otherwise = do
-    seeds :: [V.Vector Word32] <- replicateM n $ uniformVector gen 256
-    mapM initialize seeds
+      seeds :: [V.Vector Word32] <- replicateM n $ uniformVector gen 256
+      mapM initialize seeds
 
 -- TODO: Splitmix. Remove or amend these functions as soon as split mix is used
 -- and is available with the statistics package.
diff --git a/src/Mcmc/Mcmc.hs b/src/Mcmc/Mcmc.hs
--- a/src/Mcmc/Mcmc.hs
+++ b/src/Mcmc/Mcmc.hs
@@ -93,12 +93,12 @@
   | n < 0 = error "mcmcIterate: Number of iterations is negative."
   | n == 0 = return a
   | otherwise = do
-    e <- ask
-    p <- sParallelizationMode . settings <$> ask
-    -- NOTE: User interrupt is handled during iterations.
-    a' <- liftIO $ catch (aIterate p a) (mcmcExceptionHandler e a)
-    mcmcExecuteMonitors a'
-    mcmcIterate (n -1) a'
+      e <- ask
+      p <- sParallelizationMode . settings <$> ask
+      -- NOTE: User interrupt is handled during iterations.
+      a' <- liftIO $ catch (aIterate p a) (mcmcExceptionHandler e a)
+      mcmcExecuteMonitors a'
+      mcmcIterate (n - 1) a'
 
 mcmcNewRun :: Algorithm a => a -> MCMC a
 mcmcNewRun a = do
diff --git a/src/Mcmc/Monitor.hs b/src/Mcmc/Monitor.hs
--- a/src/Mcmc/Monitor.hs
+++ b/src/Mcmc/Monitor.hs
@@ -77,7 +77,7 @@
 simpleMonitor p
   | p < 1 = error "simpleMonitor: Monitor period must be 1 or larger."
   | otherwise =
-    Monitor (MonitorStdOut [] p) [] []
+      Monitor (MonitorStdOut [] p) [] []
 
 -- | Monitor to standard output; constructed with 'monitorStdOut'.
 data MonitorStdOut a = MonitorStdOut
@@ -208,19 +208,19 @@
 mfExec i (Link x p l) m
   | i `mod` mfPeriod m /= 0 = return ()
   | otherwise = case mfHandle m of
-    Nothing ->
-      error $
-        "mfExec: No handle available for monitor with name "
-          <> mfName m
-          <> "."
-    Just h ->
-      BL.hPutStrLn h $
-        mfRenderRow $
-          BL.pack (show i) :
-          renderLog p :
-          renderLog l :
-          renderLog (p * l) :
-            [BB.toLazyByteString $ mpFunc mp x | mp <- mfParams m]
+      Nothing ->
+        error $
+          "mfExec: No handle available for monitor with name "
+            <> mfName m
+            <> "."
+      Just h ->
+        BL.hPutStrLn h $
+          mfRenderRow $
+            BL.pack (show i) :
+            renderLog p :
+            renderLog l :
+            renderLog (p * l) :
+              [BB.toLazyByteString $ mpFunc mp x | mp <- mfParams m]
 
 mfClose :: MonitorFile a -> IO ()
 mfClose m = case mfHandle m of
@@ -288,26 +288,26 @@
 mbExec i t m
   | (i `mod` mbSize m /= 0) || (i == 0) = return ()
   | otherwise = case mbHandle m of
-    Nothing ->
-      error $
-        "mbExec: No handle available for batch monitor with name "
-          <> mbName m
-          <> "."
-    Just h -> do
-      xs <- takeT (mbSize m) t
-      let lps = VB.map prior xs
-          lls = VB.map likelihood xs
-          los = VB.zipWith (*) lps lls
-          mlps = mean lps
-          mlls = mean lls
-          mlos = mean los
-      BL.hPutStrLn h $
-        mfRenderRow $
-          BL.pack (show i) :
-          renderLog mlps :
-          renderLog mlls :
-          renderLog mlos :
-            [BB.toLazyByteString $ mbpFunc mbp (VB.map state xs) | mbp <- mbParams m]
+      Nothing ->
+        error $
+          "mbExec: No handle available for batch monitor with name "
+            <> mbName m
+            <> "."
+      Just h -> do
+        xs <- takeT (mbSize m) t
+        let lps = VB.map prior xs
+            lls = VB.map likelihood xs
+            los = VB.zipWith (*) lps lls
+            mlps = mean lps
+            mlls = mean lls
+            mlos = mean los
+        BL.hPutStrLn h $
+          mfRenderRow $
+            BL.pack (show i) :
+            renderLog mlps :
+            renderLog mlls :
+            renderLog mlos :
+              [BB.toLazyByteString $ mbpFunc mbp (VB.map state xs) | mbp <- mbParams m]
 
 mbClose :: MonitorBatch a -> IO ()
 mbClose m = case mbHandle m of
diff --git a/src/Mcmc/Monitor/Parameter.hs b/src/Mcmc/Monitor/Parameter.hs
--- a/src/Mcmc/Monitor/Parameter.hs
+++ b/src/Mcmc/Monitor/Parameter.hs
@@ -26,6 +26,9 @@
 import qualified Data.Double.Conversion.ByteString as BC
 import Data.Functor.Contravariant
 
+-- XXX: 'MonitorParameter' has a drawback. Extracting and monitoring multiple
+-- parameters in one go is impossible.
+
 -- | Instruction about a parameter to monitor.
 --
 -- Convert a parameter monitor from one data type to another with '(>$<)'.
diff --git a/src/Mcmc/Prior.hs b/src/Mcmc/Prior.hs
--- a/src/Mcmc/Prior.hs
+++ b/src/Mcmc/Prior.hs
@@ -161,7 +161,7 @@
 normal :: RealFloat a => Mean a -> StandardDeviation a -> PriorFunctionG a a
 normal m s x
   | s <= 0 = error "normal: Standard deviation is zero or negative."
-  | otherwise = Exp $ (- xm * xm / (2 * s * s)) - denom
+  | otherwise = Exp $ (-xm * xm / (2 * s * s)) - denom
   where
     xm = x - m
     denom = mLnSqrt2Pi + log s
diff --git a/src/Mcmc/Proposal.hs b/src/Mcmc/Proposal.hs
--- a/src/Mcmc/Proposal.hs
+++ b/src/Mcmc/Proposal.hs
@@ -14,7 +14,7 @@
 --
 -- Creation date: Wed May 20 13:42:53 2020.
 module Mcmc.Proposal
-  ( -- * Proposals and types
+  ( -- * Proposals
     PName (..),
     PDescription (..),
     PWeight (fromPWeight),
@@ -28,18 +28,21 @@
     liftProposal,
     liftProposalWith,
     ProposalSimple,
+    createProposal,
+
+    -- * Tuners
     Tuner (..),
     Tune (..),
     TuningParameter,
+    TuningFunction,
     AuxiliaryTuningParameters,
+    AuxiliaryTuningFunction,
     defaultTuningFunctionWith,
     noTuningFunction,
     noAuxiliaryTuningFunction,
-    createProposal,
     tuningParameterMin,
     tuningParameterMax,
     tuneWithTuningParameters,
-    tuneWithChainParameters,
     getOptimalRate,
 
     -- * Output
@@ -55,7 +58,6 @@
 import qualified Data.Vector as VB
 import qualified Data.Vector.Unboxed as VU
 import Lens.Micro
-import Lens.Micro.Extras
 import Mcmc.Acceptance
 import Mcmc.Internal.ByteString
 import Numeric.Log hiding (sum)
@@ -71,27 +73,30 @@
   deriving (Show, Eq, Ord)
 
 -- | The positive weight determines how often a 'Proposal' is executed per
--- iteration of the Markov chain.
+-- iteration of the Markov chain. Abstract data type; for construction, see
+-- 'pWeight'.
 newtype PWeight = PWeight {fromPWeight :: Int}
   deriving (Show, Eq, Ord)
 
 -- | Check if the weight is positive.
+--
+-- Call 'error' if weight is zero or negative.
 pWeight :: Int -> PWeight
 pWeight n
-  | n <= 0 = error "pWeight: Proposal weight is zero or negative."
+  | n <= 0 = error $ "pWeight: Proposal weight is zero or negative: " <> show n <> "."
   | otherwise = PWeight n
 
 -- | Proposal dimension.
 --
 -- The number of affected, independent parameters.
 --
--- The optimal acceptance rate of low dimensional proposals is higher than for
--- high dimensional ones.
+-- Usually, the optimal acceptance rate of low dimensional proposals is higher
+-- than for high dimensional ones. However, this is not always true (see below).
 --
--- Optimal acceptance rates are still subject to controversies. As far as I
--- know, research has focused on random walk proposals with multivariate normal
--- distributions of dimension @d@. In this case, the following acceptance rates
--- are desired:
+-- Further, optimal acceptance rates are still subject to controversies. To my
+-- knowledge, research has focused on random walk proposals with multivariate
+-- normal distributions of dimension @d@. In this case, the following acceptance
+-- rates are desired:
 --
 -- - one dimension: 0.44 (numerical results);
 --
@@ -130,8 +135,9 @@
 -- state space @a@. Essentially, it is a probability mass or probability density
 -- conditioned on the current state (i.e., a Markov kernel).
 --
--- A 'Proposal' may be tuneable in that it contains information about how to enlarge
--- or shrink the step size to tune the acceptance rate.
+-- A 'Proposal' may be tuneable in that it contains information about how to
+-- enlarge or shrink the proposal size to decrease or increase the acceptance
+-- rate.
 --
 -- Predefined proposals are provided. To create custom proposals, one may use
 -- the convenience function 'createProposal'.
@@ -165,8 +171,8 @@
 -- See also 'Jacobian'.
 --
 -- NOTE: Actually the 'Jacobian' should be part of the 'KernelRatio'. However,
--- it is more declarative to have them separate. It is a constant reminder: Is
--- the Jacobian modifier different from 1.0?
+-- it is more declarative to have them separate. Like so, we are constantly
+-- reminded: Is the Jacobian modifier different from 1.0?
 type KernelRatio = Log Double
 
 -- | Absolute value of the determinant of the Jacobian matrix.
@@ -189,7 +195,7 @@
 -- scaleFirstEntryOfTuple = _1 @~ scale
 -- @
 --
--- See also 'liftProposal' and 'liftProposalWith'.
+-- See also 'liftProposalWith'.
 infixl 7 @~
 
 (@~) :: Lens' b a -> Proposal a -> Proposal b
@@ -201,14 +207,13 @@
 
 -- | Lift a proposal from one data type to another.
 --
--- A function to calculate the Jacobian has to be provided (see also
--- 'liftProposal').
+-- A function to calculate the Jacobian has to be provided (but see '(@~)').
 --
 -- For further reference, please see the [example
 -- @Pair@](https://github.com/dschrempf/mcmc/blob/master/mcmc-examples/Pair/Pair.hs).
 liftProposalWith :: JacobianFunction b -> Lens' b a -> Proposal a -> Proposal b
 liftProposalWith jf l (Proposal n r d w s t) =
-  Proposal n r d w (liftProposalSimple jf l s) (liftTuner jf l <$> t)
+  Proposal n r d w (liftProposalSimpleWith jf l s) (liftTunerWith jf l <$> t)
 
 -- | Simple proposal without tuning information.
 --
@@ -231,8 +236,8 @@
 type ProposalSimple a = a -> GenIO -> IO (a, KernelRatio, Jacobian)
 
 -- Lift a simple proposal from one data type to another.
-liftProposalSimple :: JacobianFunction b -> Lens' b a -> ProposalSimple a -> ProposalSimple b
-liftProposalSimple jf l s = s'
+liftProposalSimpleWith :: JacobianFunction b -> Lens' b a -> ProposalSimple a -> ProposalSimple b
+liftProposalSimpleWith jf l s = s'
   where
     s' y g = do
       (x', r, j) <- s (y ^. l) g
@@ -242,19 +247,40 @@
           j' = j * jyx / jxy
       return (y', r, j')
 
+-- | Create a proposal with a single tuning parameter.
+--
+-- Proposals with arbitrary tuning parameters have to be created manually. See
+-- 'Tuner' for more information, and 'Mcmc.Proposal.Hamiltonian' for an example.
+createProposal ::
+  -- | Description of the proposal type and parameters.
+  PDescription ->
+  -- | Function creating a simple proposal for a given tuning parameter.
+  (TuningParameter -> ProposalSimple a) ->
+  -- | Dimension.
+  PDimension ->
+  -- | Name.
+  PName ->
+  -- | Weight.
+  PWeight ->
+  -- | Activate tuning?
+  Tune ->
+  Proposal a
+createProposal r f d n w Tune =
+  Proposal n r d w (f 1.0) (Just tuner)
+  where
+    fT = defaultTuningFunctionWith d
+    fTs = noAuxiliaryTuningFunction
+    g t _ = Right $ f t
+    tuner = Tuner 1.0 fT VU.empty fTs g
+createProposal r f d n w NoTune =
+  Proposal n r d w (f 1.0) Nothing
+
 -- | Required information to tune 'Proposal's.
 data Tuner a = Tuner
   { tTuningParameter :: TuningParameter,
-    -- | Instruction about how to compute new tuning parameter from a given
-    -- acceptance rate and the old tuning parameter.
-    tComputeTuningParameter :: AcceptanceRate -> TuningParameter -> TuningParameter,
+    tTuningFunction :: TuningFunction,
     tAuxiliaryTuningParameters :: AuxiliaryTuningParameters,
-    -- | Instruction about how to compute new auxiliary tuning parameters from a
-    -- given trace and the old auxiliary tuning parameters.
-    tComputeAuxiliaryTuningParameters ::
-      VB.Vector a ->
-      AuxiliaryTuningParameters ->
-      AuxiliaryTuningParameters,
+    tAuxiliaryTuningFunction :: AuxiliaryTuningFunction a,
     -- | Given the tuning parameter, and the auxiliary tuning parameters, get
     -- the tuned simple proposal.
     --
@@ -267,11 +293,11 @@
   }
 
 -- Lift tuner from one data type to another.
-liftTuner :: JacobianFunction b -> Lens' b a -> Tuner a -> Tuner b
-liftTuner jf l (Tuner p fP ps fPs g) = Tuner p fP ps fPs' g'
+liftTunerWith :: JacobianFunction b -> Lens' b a -> Tuner a -> Tuner b
+liftTunerWith jf l (Tuner p fP ps fPs g) = Tuner p fP ps fPs' g'
   where
-    fPs' = fPs . VB.map (view l)
-    g' x xs = liftProposalSimple jf l <$> g x xs
+    fPs' = fPs . VB.map (^. l)
+    g' x xs = liftProposalSimpleWith jf l <$> g x xs
 
 -- | Tune proposal?
 data Tune = Tune | NoTune
@@ -283,75 +309,49 @@
 -- expected acceptance rate; and vice versa.
 type TuningParameter = Double
 
+-- | Compute new tuning parameter from a given acceptance rate and the old
+-- tuning parameter.
+type TuningFunction = AcceptanceRate -> TuningParameter -> TuningParameter
+
 -- | Auxiliary tuning parameters; vector may be empty.
+--
+-- Auxiliary tuning parameters are not shown in proposal summaries.
 type AuxiliaryTuningParameters = VU.Vector TuningParameter
 
+-- | Compute new auxiliary tuning parameters from a given trace and the old
+-- auxiliary tuning parameters.
+type AuxiliaryTuningFunction a = VB.Vector a -> AuxiliaryTuningParameters -> AuxiliaryTuningParameters
+
 -- | Default tuning function.
 --
 -- Subject to change.
 defaultTuningFunctionWith ::
   -- Optimal acceptance rate.
   PDimension ->
-  AcceptanceRate ->
-  TuningParameter ->
-  TuningParameter
+  TuningFunction
 defaultTuningFunctionWith d r t = let rO = getOptimalRate d in exp (2 * (r - rO)) * t
 
--- | Do no tune.
+-- | Do not tune.
 --
 -- Useful if auxiliary tuning parameters are tuned, but not the main tuning
 -- parameter.
-noTuningFunction :: AcceptanceRate -> TuningParameter -> TuningParameter
+noTuningFunction :: TuningFunction
 noTuningFunction _ = id
 
 -- | Do not tune auxiliary parameters.
-noAuxiliaryTuningFunction :: VB.Vector a -> AuxiliaryTuningParameters -> AuxiliaryTuningParameters
+noAuxiliaryTuningFunction :: AuxiliaryTuningFunction a
 noAuxiliaryTuningFunction _ = id
 
--- | Create a proposal with a single tuning parameter.
---
--- Proposals with arbitrary tuning parameters have to be created manually. See
--- 'Tuner' for more information, and 'Mcmc.Proposal.Hamiltonian' for an example.
-createProposal ::
-  -- | Description of the proposal type and parameters.
-  PDescription ->
-  -- | Function creating a simple proposal for a given tuning parameter.
-  (TuningParameter -> ProposalSimple a) ->
-  -- | Dimension.
-  PDimension ->
-  -- | Name.
-  PName ->
-  -- | Weight.
-  PWeight ->
-  -- | Activate tuning?
-  Tune ->
-  Proposal a
-createProposal r f d n w Tune =
-  Proposal n r d w (f 1.0) (Just tuner)
-  where
-    fT = defaultTuningFunctionWith d
-    fTs = noAuxiliaryTuningFunction
-    g t _ = Right $ f t
-    tuner = Tuner 1.0 fT VU.empty fTs g
-createProposal r f d n w NoTune =
-  Proposal n r d w (f 1.0) Nothing
-
 -- IDEA: Per proposal type tuning parameter boundaries. For example, a sliding
 -- proposal with a large tuning parameter is not a problem. But then, if the
 -- tuning parameters are very different from one, a different base proposal
 -- should be chosen.
 
--- | Minimal tuning parameter; @1e-5@, subject to change.
---
--- >>> tuningParameterMin
--- 1e-5
+-- | Minimal tuning parameter; subject to change.
 tuningParameterMin :: TuningParameter
 tuningParameterMin = 1e-5
 
--- | Maximal tuning parameter; @1e3@, subject to change.
---
--- >>> tuningParameterMax
--- 1e3
+-- | Maximal tuning parameter; subject to change.
 tuningParameterMax :: TuningParameter
 tuningParameterMax = 1e3
 
@@ -368,6 +368,8 @@
 -- - the 'Proposal' is not tuneable;
 --
 -- - the auxiliary tuning parameters are invalid.
+--
+-- Used by 'Mcmc.Chain.Save.fromSavedChain'.
 tuneWithTuningParameters ::
   TuningParameter ->
   AuxiliaryTuningParameters ->
@@ -383,15 +385,6 @@
      in case psE of
           Left err -> Left $ "tune: " <> err
           Right ps -> Right $ p {prSimple = ps, prTuner = Just $ Tuner t'' fT ts fTs g}
-
--- | See 'tuneWithTuningParameters' and 'Tuner'.
-tuneWithChainParameters :: AcceptanceRate -> VB.Vector a -> Proposal a -> Either String (Proposal a)
-tuneWithChainParameters ar xs p = case prTuner p of
-  Nothing -> Left "tuneWithChainParameters: Proposal is not tunable."
-  Just (Tuner t fT ts fTs _) ->
-    let t' = fT ar t
-        ts' = fTs xs ts
-     in tuneWithTuningParameters t' ts' p
 
 -- | See 'PDimension'.
 getOptimalRate :: PDimension -> Double
diff --git a/src/Mcmc/Proposal/Bactrian.hs b/src/Mcmc/Proposal/Bactrian.hs
--- a/src/Mcmc/Proposal/Bactrian.hs
+++ b/src/Mcmc/Proposal/Bactrian.hs
@@ -40,14 +40,14 @@
       d = normalDistr mn sd
   x <- genContVar d g
   b <- bernoulli 0.5 g
-  return $ if b then x else - x
+  return $ if b then x else -x
 
 logDensityBactrian :: SpikeParameter -> StandardDeviation Double -> Double -> Log Double
 logDensityBactrian m s x = Exp $ log $ kernel1 + kernel2
   where
     mn = m * s
     sd = sqrt (1 - m * m) * s
-    dist1 = normalDistr (- mn) sd
+    dist1 = normalDistr (-mn) sd
     dist2 = normalDistr mn sd
     kernel1 = density dist1 x
     kernel2 = density dist2 x
diff --git a/src/Mcmc/Proposal/Hamiltonian.hs b/src/Mcmc/Proposal/Hamiltonian.hs
--- a/src/Mcmc/Proposal/Hamiltonian.hs
+++ b/src/Mcmc/Proposal/Hamiltonian.hs
@@ -333,14 +333,14 @@
   Maybe (Positions, Momenta)
 leapfrog grad mVal hMassesInvEps l eps theta phi = do
   let -- The first half step of the momenta.
-      phiHalf = leapfrogStepMomenta 0.5 eps grad theta phi
+      phiHalf = leapfrogStepMomenta (0.5 * eps) grad theta phi
   -- L-1 full steps. This gives the positions theta_{L-1}, and the momenta
   -- phi_{L-1/2}.
   (thetaLM1, phiLM1Half) <- go (l - 1) (Just (theta, phiHalf))
   -- The last full step of the positions.
   thetaL <- valF $ leapfrogStepPositions hMassesInvEps thetaLM1 phiLM1Half
   let -- The last half step of the momenta.
-      phiL = leapfrogStepMomenta 0.5 eps grad thetaL phiLM1Half
+      phiL = leapfrogStepMomenta (0.5 * eps) grad thetaL phiLM1Half
   return (thetaL, phiL)
   where
     valF x = case mVal of
@@ -350,14 +350,13 @@
     go 0 (Just (t, p)) = Just (t, p)
     go n (Just (t, p)) =
       let t' = leapfrogStepPositions hMassesInvEps t p
-          p' = leapfrogStepMomenta 1.0 eps grad t' p
+          p' = leapfrogStepMomenta eps grad t' p
           r = (,p') <$> valF t'
        in go (n - 1) r
 
 leapfrogStepMomenta ::
-  -- Size of step (half or full step).
+  -- Step size (usually a multiple of the leapfrog scaling factor).
   Double ->
-  LeapfrogScalingFactor ->
   Gradient Positions ->
   -- Current positions.
   Positions ->
@@ -365,7 +364,7 @@
   Momenta ->
   -- New momenta.
   Momenta
-leapfrogStepMomenta xi eps grad theta phi = phi + L.scale (xi * eps) (grad theta)
+leapfrogStepMomenta eps grad theta phi = phi + L.scale eps (grad theta)
 
 leapfrogStepPositions ::
   HMassesInvEps ->
@@ -394,14 +393,14 @@
   Either String (HSettings a)
 hTuningParametersToSettings s t ts
   | nTsNotOK =
-    Left "hTuningParametersToSettings: Auxiliary variables do not have correct dimension."
+      Left "hTuningParametersToSettings: Auxiliary variables do not have correct dimension."
   | otherwise =
-    Right $
-      s
-        { hMasses = msTuned,
-          hLeapfrogTrajectoryLength = lTuned,
-          hLeapfrogScalingFactor = eTuned
-        }
+      Right $
+        s
+          { hMasses = msTuned,
+            hLeapfrogTrajectoryLength = lTuned,
+            hLeapfrogScalingFactor = eTuned
+          }
   where
     ms = hMasses s
     d = L.rows $ L.unSym ms
@@ -519,16 +518,14 @@
 tuneDiagonalMassesOnly ::
   Int ->
   (a -> Positions) ->
-  VB.Vector a ->
-  AuxiliaryTuningParameters ->
-  AuxiliaryTuningParameters
+  AuxiliaryTuningFunction a
 tuneDiagonalMassesOnly dim toVec xs ts
   -- If not enough data is available, do not tune.
   | VB.length xs < samplesMinDiagonal = ts
   | otherwise =
-    -- Replace the diagonal.
-    massesToTuningParameters $
-      L.trustSym $ massesOld - L.diag massesDiagonalOld + L.diag massesDiagonalNew
+      -- Replace the diagonal.
+      massesToTuningParameters $
+        L.trustSym $ massesOld - L.diag massesDiagonalOld + L.diag massesDiagonalNew
   where
     -- xs: Each vector entry contains all parameter values of one iteration.
     -- xs': Each row contains all parameter values of one iteration.
@@ -550,9 +547,7 @@
 tuneAllMasses ::
   Int ->
   (a -> Positions) ->
-  VB.Vector a ->
-  AuxiliaryTuningParameters ->
-  AuxiliaryTuningParameters
+  AuxiliaryTuningFunction a
 tuneAllMasses dim toVec xs ts
   -- If not enough data is available, do not tune.
   | VB.length xs < samplesMinDiagonal = ts
diff --git a/src/Mcmc/Proposal/Slide.hs b/src/Mcmc/Proposal/Slide.hs
--- a/src/Mcmc/Proposal/Slide.hs
+++ b/src/Mcmc/Proposal/Slide.hs
@@ -67,7 +67,7 @@
 -- The actual proposal with tuning parameter.
 slideUniformSimple :: Size -> TuningParameter -> ProposalSimple Double
 slideUniformSimple d t =
-  genericContinuous (uniformDistr (- t * d) (t * d)) (+) Nothing Nothing
+  genericContinuous (uniformDistr (-t * d) (t * d)) (+) Nothing Nothing
 
 -- | See 'slide'.
 --
diff --git a/src/Mcmc/Settings.hs b/src/Mcmc/Settings.hs
--- a/src/Mcmc/Settings.hs
+++ b/src/Mcmc/Settings.hs
@@ -316,12 +316,12 @@
   | not $ burnInValid bi = serr $ "Burn in setting invalid: " <> show bi <> "."
   | fromIterations i < 0 = serr "Number of iterations is negative."
   | burnInIterations bi + fromIterations i - iCurrent < 0 =
-    serr "Current iteration is larger than the total number of iterations."
+      serr "Current iteration is larger than the total number of iterations."
   | not $ validTraceLength tl = serr $ "Trace length invalid: " <> show tl <> "."
   | iCurrent /= 0 && em /= Continue =
-    serr "Current iteration is non-zero but execution mode is not 'Continue'."
+      serr "Current iteration is non-zero but execution mode is not 'Continue'."
   | iCurrent == 0 && em == Continue =
-    serr "Current iteration is zero but execution mode is 'Continue'."
+      serr "Current iteration is zero but execution mode is 'Continue'."
   | otherwise = return ()
   where
     serr = settingsError s iCurrent