diff --git a/LICENSE.md b/LICENSE.md
new file mode 100644
--- /dev/null
+++ b/LICENSE.md
@@ -0,0 +1,355 @@
+Mozilla Public License Version 2.0
+==================================
+
+### 1. Definitions
+
+**1.1. “Contributor”**
+    means each individual or legal entity that creates, contributes to
+    the creation of, or owns Covered Software.
+
+**1.2. “Contributor Version”**
+    means the combination of the Contributions of others (if any) used
+    by a Contributor and that particular Contributor's Contribution.
+
+**1.3. “Contribution”**
+    means Covered Software of a particular Contributor.
+
+**1.4. “Covered Software”**
+    means Source Code Form to which the initial Contributor has attached
+    the notice in Exhibit A, the Executable Form of such Source Code
+    Form, and Modifications of such Source Code Form, in each case
+    including portions thereof.
+
+**1.5. “Incompatible With Secondary Licenses”**
+    means
+
+* **(a)** that the initial Contributor has attached the notice described
+    in Exhibit B to the Covered Software; or
+* **(b)** that the Covered Software was made available under the terms of
+    version 1.1 or earlier of the License, but not also under the
+    terms of a Secondary License.
+
+**1.6. “Executable Form”**
+    means any form of the work other than Source Code Form.
+
+**1.7. “Larger Work”**
+    means a work that combines Covered Software with other material, in
+    a separate file or files, that is not Covered Software.
+
+**1.8. “License”**
+    means this document.
+
+**1.9. “Licensable”**
+    means having the right to grant, to the maximum extent possible,
+    whether at the time of the initial grant or subsequently, any and
+    all of the rights conveyed by this License.
+
+**1.10. “Modifications”**
+    means any of the following:
+
+* **(a)** any file in Source Code Form that results from an addition to,
+    deletion from, or modification of the contents of Covered
+    Software; or
+* **(b)** any new file in Source Code Form that contains any Covered
+    Software.
+
+**1.11. “Patent Claims” of a Contributor**
+    means any patent claim(s), including without limitation, method,
+    process, and apparatus claims, in any patent Licensable by such
+    Contributor that would be infringed, but for the grant of the
+    License, by the making, using, selling, offering for sale, having
+    made, import, or transfer of either its Contributions or its
+    Contributor Version.
+
+**1.12. “Secondary License”**
+    means either the GNU General Public License, Version 2.0, the GNU
+    Lesser General Public License, Version 2.1, the GNU Affero General
+    Public License, Version 3.0, or any later versions of those
+    licenses.
+
+**1.13. “Source Code Form”**
+    means the form of the work preferred for making modifications.
+
+**1.14. “You” (or “Your”)**
+    means an individual or a legal entity exercising rights under this
+    License. For legal entities, “You” includes any entity that
+    controls, is controlled by, or is under common control with You. For
+    purposes of this definition, “control” means **(a)** the power, direct
+    or indirect, to cause the direction or management of such entity,
+    whether by contract or otherwise, or **(b)** ownership of more than
+    fifty percent (50%) of the outstanding shares or beneficial
+    ownership of such entity.
+
+
+### 2. License Grants and Conditions
+
+#### 2.1. Grants
+
+Each Contributor hereby grants You a world-wide, royalty-free,
+non-exclusive license:
+
+* **(a)** under intellectual property rights (other than patent or trademark)
+    Licensable by such Contributor to use, reproduce, make available,
+    modify, display, perform, distribute, and otherwise exploit its
+    Contributions, either on an unmodified basis, with Modifications, or
+    as part of a Larger Work; and
+* **(b)** under Patent Claims of such Contributor to make, use, sell, offer
+    for sale, have made, import, and otherwise transfer either its
+    Contributions or its Contributor Version.
+
+#### 2.2. Effective Date
+
+The licenses granted in Section 2.1 with respect to any Contribution
+become effective for each Contribution on the date the Contributor first
+distributes such Contribution.
+
+#### 2.3. Limitations on Grant Scope
+
+The licenses granted in this Section 2 are the only rights granted under
+this License. No additional rights or licenses will be implied from the
+distribution or licensing of Covered Software under this License.
+Notwithstanding Section 2.1(b) above, no patent license is granted by a
+Contributor:
+
+* **(a)** for any code that a Contributor has removed from Covered Software;
+    or
+* **(b)** for infringements caused by: **(i)** Your and any other third party's
+    modifications of Covered Software, or **(ii)** the combination of its
+    Contributions with other software (except as part of its Contributor
+    Version); or
+* **(c)** under Patent Claims infringed by Covered Software in the absence of
+    its Contributions.
+
+This License does not grant any rights in the trademarks, service marks,
+or logos of any Contributor (except as may be necessary to comply with
+the notice requirements in Section 3.4).
+
+#### 2.4. Subsequent Licenses
+
+No Contributor makes additional grants as a result of Your choice to
+distribute the Covered Software under a subsequent version of this
+License (see Section 10.2) or under the terms of a Secondary License (if
+permitted under the terms of Section 3.3).
+
+#### 2.5. Representation
+
+Each Contributor represents that the Contributor believes its
+Contributions are its original creation(s) or it has sufficient rights
+to grant the rights to its Contributions conveyed by this License.
+
+#### 2.6. Fair Use
+
+This License is not intended to limit any rights You have under
+applicable copyright doctrines of fair use, fair dealing, or other
+equivalents.
+
+#### 2.7. Conditions
+
+Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted
+in Section 2.1.
+
+
+### 3. Responsibilities
+
+#### 3.1. Distribution of Source Form
+
+All distribution of Covered Software in Source Code Form, including any
+Modifications that You create or to which You contribute, must be under
+the terms of this License. You must inform recipients that the Source
+Code Form of the Covered Software is governed by the terms of this
+License, and how they can obtain a copy of this License. You may not
+attempt to alter or restrict the recipients' rights in the Source Code
+Form.
+
+#### 3.2. Distribution of Executable Form
+
+If You distribute Covered Software in Executable Form then:
+
+* **(a)** such Covered Software must also be made available in Source Code
+    Form, as described in Section 3.1, and You must inform recipients of
+    the Executable Form how they can obtain a copy of such Source Code
+    Form by reasonable means in a timely manner, at a charge no more
+    than the cost of distribution to the recipient; and
+
+* **(b)** You may distribute such Executable Form under the terms of this
+    License, or sublicense it under different terms, provided that the
+    license for the Executable Form does not attempt to limit or alter
+    the recipients' rights in the Source Code Form under this License.
+
+#### 3.3. Distribution of a Larger Work
+
+You may create and distribute a Larger Work under terms of Your choice,
+provided that You also comply with the requirements of this License for
+the Covered Software. If the Larger Work is a combination of Covered
+Software with a work governed by one or more Secondary Licenses, and the
+Covered Software is not Incompatible With Secondary Licenses, this
+License permits You to additionally distribute such Covered Software
+under the terms of such Secondary License(s), so that the recipient of
+the Larger Work may, at their option, further distribute the Covered
+Software under the terms of either this License or such Secondary
+License(s).
+
+#### 3.4. Notices
+
+You may not remove or alter the substance of any license notices
+(including copyright notices, patent notices, disclaimers of warranty,
+or limitations of liability) contained within the Source Code Form of
+the Covered Software, except that You may alter any license notices to
+the extent required to remedy known factual inaccuracies.
+
+#### 3.5. Application of Additional Terms
+
+You may choose to offer, and to charge a fee for, warranty, support,
+indemnity or liability obligations to one or more recipients of Covered
+Software. However, You may do so only on Your own behalf, and not on
+behalf of any Contributor. You must make it absolutely clear that any
+such warranty, support, indemnity, or liability obligation is offered by
+You alone, and You hereby agree to indemnify every Contributor for any
+liability incurred by such Contributor as a result of warranty, support,
+indemnity or liability terms You offer. You may include additional
+disclaimers of warranty and limitations of liability specific to any
+jurisdiction.
+
+
+### 4. Inability to Comply Due to Statute or Regulation
+
+If it is impossible for You to comply with any of the terms of this
+License with respect to some or all of the Covered Software due to
+statute, judicial order, or regulation then You must: **(a)** comply with
+the terms of this License to the maximum extent possible; and **(b)**
+describe the limitations and the code they affect. Such description must
+be placed in a text file included with all distributions of the Covered
+Software under this License. Except to the extent prohibited by statute
+or regulation, such description must be sufficiently detailed for a
+recipient of ordinary skill to be able to understand it.
+
+
+### 5. Termination
+
+**5.1.** The rights granted under this License will terminate automatically
+if You fail to comply with any of its terms. However, if You become
+compliant, then the rights granted under this License from a particular
+Contributor are reinstated **(a)** provisionally, unless and until such
+Contributor explicitly and finally terminates Your grants, and **(b)** on an
+ongoing basis, if such Contributor fails to notify You of the
+non-compliance by some reasonable means prior to 60 days after You have
+come back into compliance. Moreover, Your grants from a particular
+Contributor are reinstated on an ongoing basis if such Contributor
+notifies You of the non-compliance by some reasonable means, this is the
+first time You have received notice of non-compliance with this License
+from such Contributor, and You become compliant prior to 30 days after
+Your receipt of the notice.
+
+**5.2.** If You initiate litigation against any entity by asserting a patent
+infringement claim (excluding declaratory judgment actions,
+counter-claims, and cross-claims) alleging that a Contributor Version
+directly or indirectly infringes any patent, then the rights granted to
+You by any and all Contributors for the Covered Software under Section
+2.1 of this License shall terminate.
+
+**5.3.** In the event of termination under Sections 5.1 or 5.2 above, all
+end user license agreements (excluding distributors and resellers) which
+have been validly granted by You or Your distributors under this License
+prior to termination shall survive termination.
+
+
+### 6. Disclaimer of Warranty
+
+> Covered Software is provided under this License on an “as is”
+> basis, without warranty of any kind, either expressed, implied, or
+> statutory, including, without limitation, warranties that the
+> Covered Software is free of defects, merchantable, fit for a
+> particular purpose or non-infringing. The entire risk as to the
+> quality and performance of the Covered Software is with You.
+> Should any Covered Software prove defective in any respect, You
+> (not any Contributor) assume the cost of any necessary servicing,
+> repair, or correction. This disclaimer of warranty constitutes an
+> essential part of this License. No use of any Covered Software is
+> authorized under this License except under this disclaimer.
+
+### 7. Limitation of Liability
+
+> Under no circumstances and under no legal theory, whether tort
+> (including negligence), contract, or otherwise, shall any
+> Contributor, or anyone who distributes Covered Software as
+> permitted above, be liable to You for any direct, indirect,
+> special, incidental, or consequential damages of any character
+> including, without limitation, damages for lost profits, loss of
+> goodwill, work stoppage, computer failure or malfunction, or any
+> and all other commercial damages or losses, even if such party
+> shall have been informed of the possibility of such damages. This
+> limitation of liability shall not apply to liability for death or
+> personal injury resulting from such party's negligence to the
+> extent applicable law prohibits such limitation. Some
+> jurisdictions do not allow the exclusion or limitation of
+> incidental or consequential damages, so this exclusion and
+> limitation may not apply to You.
+
+
+### 8. Litigation
+
+Any litigation relating to this License may be brought only in the
+courts of a jurisdiction where the defendant maintains its principal
+place of business and such litigation shall be governed by laws of that
+jurisdiction, without reference to its conflict-of-law provisions.
+Nothing in this Section shall prevent a party's ability to bring
+cross-claims or counter-claims.
+
+
+### 9. Miscellaneous
+
+This License represents the complete agreement concerning the subject
+matter hereof. If any provision of this License is held to be
+unenforceable, such provision shall be reformed only to the extent
+necessary to make it enforceable. Any law or regulation which provides
+that the language of a contract shall be construed against the drafter
+shall not be used to construe this License against a Contributor.
+
+
+### 10. Versions of the License
+
+#### 10.1. New Versions
+
+Mozilla Foundation is the license steward. Except as provided in Section
+10.3, no one other than the license steward has the right to modify or
+publish new versions of this License. Each version will be given a
+distinguishing version number.
+
+#### 10.2. Effect of New Versions
+
+You may distribute the Covered Software under the terms of the version
+of the License under which You originally received the Covered Software,
+or under the terms of any subsequent version published by the license
+steward.
+
+#### 10.3. Modified Versions
+
+If you create software not governed by this License, and you want to
+create a new license for such software, you may create and use a
+modified version of this License if you rename the license and remove
+any references to the name of the license steward (except to note that
+such modified license differs from this License).
+
+#### 10.4. Distributing Source Code Form that is Incompatible With Secondary Licenses
+
+If You choose to distribute Source Code Form that is Incompatible With
+Secondary Licenses under the terms of this version of the License, the
+notice described in Exhibit B of this License must be attached.
+
+## Exhibit A - Source Code Form License Notice
+
+    This Source Code Form is subject to the terms of the Mozilla Public
+    License, v. 2.0. If a copy of the MPL was not distributed with this
+    file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+If it is not possible or desirable to put the notice in a particular
+file, then You may include the notice in a location (such as a LICENSE
+file in a relevant directory) where a recipient would be likely to look
+for such a notice.
+
+You may add additional accurate notices of copyright ownership.
+
+## Exhibit B - “Incompatible With Secondary Licenses” Notice
+
+    This Source Code Form is "Incompatible With Secondary Licenses", as
+    defined by the Mozilla Public License, v. 2.0.
diff --git a/README.md b/README.md
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--- /dev/null
+++ b/README.md
@@ -0,0 +1,4 @@
+# `detour-via-sci`
+
+For encoding and decoding newtype rationals as scientific with a fixed number
+of decimal places.
diff --git a/Setup.hs b/Setup.hs
new file mode 100644
--- /dev/null
+++ b/Setup.hs
@@ -0,0 +1,7 @@
+-- This script is used to build and install your package. Typically you don't
+-- need to change it. The Cabal documentation has more information about this
+-- file: <https://www.haskell.org/cabal/users-guide/installing-packages.html>.
+import qualified Distribution.Simple
+
+main :: IO ()
+main = Distribution.Simple.defaultMain
diff --git a/changelog.md b/changelog.md
new file mode 100644
--- /dev/null
+++ b/changelog.md
@@ -0,0 +1,10 @@
+# 1.0.0
+
+Initial version with;
+
+* `toSci` and `fromSci` for converting Rational to and from Scientific.
+* `showSci` for showing Rational as if Scientific.
+* For JSON, instances of `ToJSON` and `FromJSON` for newtype Rational that also
+  have instances of `DefaultDecimalPlaces` and `NewType`.
+* For CSV, instances of `ToField` and `FromField` in the same way.
+* Template Haskell functions to generate instances.
diff --git a/detour-via-sci.cabal b/detour-via-sci.cabal
new file mode 100644
--- /dev/null
+++ b/detour-via-sci.cabal
@@ -0,0 +1,91 @@
+-- This file has been generated from package.dhall by hpack version 0.27.0.
+--
+-- see: https://github.com/sol/hpack
+--
+-- hash: 2f32f936e96f484d95a230c305f154b0131c239d1579d13f2412c8e659930bec
+
+name:           detour-via-sci
+version:        1.0.0
+synopsis:       JSON and CSV encoding for rationals as decimal point numbers.
+description:    Lossy JSON and CSV encoding and decoding for newtype rationals via scientific with fixed decimal places.
+category:       data, math, numeric, json, csv
+homepage:       https://github.com/blockscope/flare-timing/tree/master/detour-via-sci#readme
+bug-reports:    https://github.com/blockscope/flare-timing/issues
+author:         Phil de Joux
+maintainer:     phil.dejoux@blockscope.com
+copyright:      © 2017-2018 Phil de Joux, © 2017-2018 Block Scope Limited
+license:        MPL-2.0
+license-file:   LICENSE.md
+tested-with:    GHC == 8.2.2
+build-type:     Simple
+cabal-version:  >= 1.10
+
+extra-source-files:
+    changelog.md
+    package.dhall
+    README.md
+
+source-repository head
+  type: git
+  location: https://github.com/blockscope/flare-timing
+  subdir: detour-via-sci
+
+library
+  exposed-modules:
+      Data.Via.Scientific
+  other-modules:
+      Paths_detour_via_sci
+  hs-source-dirs:
+      library
+  ghc-options: -Wall
+  build-depends:
+      aeson
+    , base >=4.5 && <5
+    , cassava
+    , newtype
+    , scientific
+    , siggy-chardust
+    , template-haskell
+  default-language: Haskell2010
+
+test-suite doctest
+  type: exitcode-stdio-1.0
+  main-is: DocTest.hs
+  other-modules:
+      Data.Via.Scientific
+      Paths_detour_via_sci
+  hs-source-dirs:
+      library
+      test-suite-doctest
+  ghc-options: -Wall -rtsopts -threaded -with-rtsopts=-N
+  build-depends:
+      aeson
+    , base
+    , cassava
+    , doctest
+    , newtype
+    , scientific
+    , siggy-chardust
+    , template-haskell
+  default-language: Haskell2010
+
+test-suite hlint
+  type: exitcode-stdio-1.0
+  main-is: HLint.hs
+  other-modules:
+      Data.Via.Scientific
+      Paths_detour_via_sci
+  hs-source-dirs:
+      library
+      test-suite-hlint
+  ghc-options: -Wall -rtsopts -threaded -with-rtsopts=-N
+  build-depends:
+      aeson
+    , base
+    , cassava
+    , hlint
+    , newtype
+    , scientific
+    , siggy-chardust
+    , template-haskell
+  default-language: Haskell2010
diff --git a/library/Data/Via/Scientific.hs b/library/Data/Via/Scientific.hs
new file mode 100644
--- /dev/null
+++ b/library/Data/Via/Scientific.hs
@@ -0,0 +1,284 @@
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE UndecidableInstances #-}
+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE DeriveLift #-}
+
+{-|
+Module: Data.Via.Scientific
+Copyright:
+    © 2018 Phil de Joux
+    © 2018 Block Scope Limited
+License: MPL-2.0
+Maintainer: Phil de Joux <phil.dejoux@blockscope.com>
+Stability: experimental
+
+For encoding and decoding newtype rationals as scientific with a fixed number
+of decimal places.
+-}
+module Data.Via.Scientific
+    (
+    -- * Usage
+    -- $use
+    
+    -- * Decimal Places
+      DecimalPlaces(..)
+    , ViaSci(..)
+    , DefaultDecimalPlaces(..)
+    , dpDegree
+    , showSci
+    -- * Conversions
+    , fromSci
+    , toSci
+    -- * Deriving instances with Template Haskell
+    , deriveDecimalPlaces
+    , deriveJsonViaSci
+    , deriveCsvViaSci
+    ) where
+
+import Control.Newtype (Newtype(..))
+import Control.Applicative (empty)
+import Data.Aeson (ToJSON(..), FromJSON(..), Value(Number))
+import Data.Csv (ToField(..), FromField(..))
+import Data.Scientific
+    ( Scientific
+    , FPFormat(..)
+    , toRealFloat
+    , fromRationalRepetend
+    , formatScientific
+    )
+import Language.Haskell.TH (Q, Name, Dec, conT)
+import Language.Haskell.TH.Syntax
+import Data.Ratio.Rounding (dpRound)
+
+-- | A choice of 8 decimal places for
+-- <https://en.wikipedia.org/wiki/Decimal_degrees decimal degrees> is just
+-- a bit more than a mm at the equator and less elsewhere.
+--
+--     * 1.1132 mm at the equator
+--     * 1.0247 mm at 23° N/S
+--     * 787.1 µm at 45° N/S
+--     * 434.96 µm at 67° N/S
+dpDegree :: DecimalPlaces
+dpDegree = DecimalPlaces 8
+
+-- NOTE: For deriving Lift, see https://ghc.haskell.org/trac/ghc/ticket/14296
+-- | A positive number of decimal places.
+newtype DecimalPlaces = DecimalPlaces Int deriving (Show, Lift)
+
+-- | From 'Scientific' exactly to 'Rational'.
+--
+-- >>> let x = 0.1122334455667788
+-- >>> fromSci x
+-- 4043636029064415 % 36028797018963968
+-- >>> x == fromRational (fromSci x)
+-- True
+fromSci :: Scientific -> Rational
+fromSci x = toRational (toRealFloat x :: Double)
+
+-- | To 'Scientific' from 'Rational' as near as possible up to the given number
+-- of 'DecimalPlaces' with rounding.
+--
+-- >>> let x = 1122334455667788 % 10000000000000000
+-- >>> toSci (DecimalPlaces 8) x
+-- 0.11223345
+-- >>> x == toRational (toSci (DecimalPlaces 8) x)
+-- False
+-- >>> x == toRational (toSci (DecimalPlaces 16) x)
+-- True
+-- >>> x == toRational (toSci (DecimalPlaces 32) x)
+-- True
+toSci :: DecimalPlaces -> Rational -> Scientific
+toSci (DecimalPlaces dp) x =
+    let y = dpRound (toInteger dp) x
+    in case fromRationalRepetend (Just $ dp + 1) y of
+        Left (s, _) -> s
+        Right (s, _) -> s
+
+-- | Shows a 'Scientific' value with a fixed number of decimal places.
+--
+-- >>> let x = 0.1122334455667788
+-- >>> showSci (DecimalPlaces 16) x
+-- "0.1122334455667788"
+-- >>> showSci (DecimalPlaces 8) x
+-- "0.11223345"
+-- >>> showSci (DecimalPlaces 4) x
+-- "0.1122"
+-- >>> showSci (DecimalPlaces 1) x
+-- "0.1"
+-- >>> showSci (DecimalPlaces 0) x
+-- "0"
+-- >>> showSci (DecimalPlaces (-1)) x
+-- "0"
+-- >>> showSci (DecimalPlaces 32) x
+-- "0.11223344556677880000000000000000"
+showSci :: DecimalPlaces -> Scientific -> String
+showSci (DecimalPlaces dp) =
+    formatScientific Fixed (Just dp)
+
+-- | A default number of decimal places for a type.
+class DefaultDecimalPlaces a where
+    defdp :: a -> DecimalPlaces
+    defdp _ = DecimalPlaces 0
+
+-- | An intermediate type used during encoding to JSON with @aeson@ and during
+-- encoding to CSV with @cassava@. It's also used during decoding.
+--
+-- The original type, a newtype 'Rational', goes to and fro __via__
+-- __sci__entific so that the rational value can be encoded as a scientific
+-- value with a fixed number of decimal places.
+data ViaSci n where
+    ViaSci
+        :: (DefaultDecimalPlaces n, Newtype n Rational)
+        => n 
+        -> ViaSci n
+
+deriving instance (Eq n) => Eq (ViaSci n)
+deriving instance (Ord n) => Ord (ViaSci n)
+deriving instance (Show n) => Show (ViaSci n)
+
+instance
+    (DefaultDecimalPlaces n, Newtype n Rational)
+    => ToJSON (ViaSci n) where
+    toJSON (ViaSci x) = Number $ toSci (defdp x) (unpack x)
+
+instance
+    (DefaultDecimalPlaces n, Newtype n Rational)
+    => FromJSON (ViaSci n) where
+    parseJSON x@(Number _) = ViaSci <$> (pack . fromSci <$> parseJSON x)
+    parseJSON _ = empty
+
+instance
+    (DefaultDecimalPlaces n, Newtype n Rational)
+    => ToField (ViaSci n) where
+    toField (ViaSci x) = toField $ toSci (defdp x) (unpack x)
+
+instance
+    (DefaultDecimalPlaces n, Newtype n Rational)
+    => FromField (ViaSci n) where
+    parseField x = ViaSci <$> (pack . fromSci <$> parseField x)
+
+-- SEE: https://markkarpov.com/tutorial/th.html
+-- | Taking a number of decimal places from the given 'DecimalPlaces' newtype,
+-- derives an instance of 'DefaultDecimalPlaces'.
+--
+-- >>> deriveDecimalPlaces (DecimalPlaces 8) ''Lat
+-- ...
+deriveDecimalPlaces :: DecimalPlaces -> Name -> Q [Dec]
+deriveDecimalPlaces dp name =
+    [d|
+        instance DefaultDecimalPlaces $(conT name) where
+            defdp _ = $(lift dp)
+        |]
+
+-- | Derives an instance of 'ToJSON' wrapping the value with 'ViaSci' before
+-- encoding. Similarly the value is decoded as 'ViaSci' and then unwrapped in
+-- the derived instance of 'FromJSON'.
+-- 
+-- >>> deriveJsonViaSci ''Lat
+-- ...
+deriveJsonViaSci :: Name -> Q [Dec]
+deriveJsonViaSci name =
+    [d|
+        instance ToJSON $a where
+            toJSON x = toJSON $ ViaSci x
+
+        instance FromJSON $a where
+            parseJSON o = do
+                ViaSci x <- parseJSON o
+                return x
+        |]
+    where
+        a = conT name
+
+-- | Similar to 'deriveJsonViaSci' but for instances of 'ToField' and 'FromField'.
+--
+-- >>> deriveCsvViaSci ''Lat
+-- ...
+deriveCsvViaSci :: Name -> Q [Dec]
+deriveCsvViaSci name =
+    [d|
+        instance ToField $a where
+            toField = toField . ViaSci
+
+        instance FromField $a where
+            parseField c = do
+                ViaSci x <- parseField c
+                return x
+        |]
+    where
+        a = conT name
+
+-- $setup
+-- >>> :set -XOverloadedStrings
+-- >>> :set -XTemplateHaskell
+-- >>> :set -XFlexibleInstances
+-- >>> :set -XMultiParamTypeClasses
+-- >>> import Data.Ratio ((%))
+-- >>> import Data.Aeson (encode, decode)
+-- >>> import Data.Text (Text)
+-- >>> import Data.Vector (Vector, fromList)
+-- >>> import qualified Data.Csv as Csv (HasHeader(..), encode, decode)
+-- >>> import Control.Newtype (Newtype(..))
+-- >>> instance Show (Q [a]) where show _ = "..."
+
+-- $use
+-- Let's say we have a latitude that is a @newtype@ 'Rational' number but we
+-- want it to be encoded to JSON with a fixed number of decimal places.
+--
+-- >>> newtype Lat = Lat Rational deriving (Eq, Ord, Show)
+--
+-- Types going 'ViaSci' also need to be instances of 'DefaultDecimalPlaces' and
+-- 'Newtype'.
+--
+-- >>> :{
+-- instance DefaultDecimalPlaces Lat where
+--     defdp _ = DecimalPlaces 8
+-- instance Newtype Lat Rational where
+--     pack = Lat
+--     unpack (Lat a) = a
+-- instance ToJSON Lat where
+--     toJSON x = toJSON $ ViaSci x
+-- instance FromJSON Lat where
+--     parseJSON o = do ViaSci x <- parseJSON o; return x
+-- :}
+--
+-- >>> let x = 1122334455667788 % 10000000000000000
+-- >>> fromRational x
+-- 0.1122334455667788
+-- >>> toSci (DecimalPlaces 8) x
+-- 0.11223345
+-- 
+-- When having to check numbers by hand, a fixed decimal is more familiar than
+-- a ratio of possibly large integers.
+-- 
+-- >>> encode x
+-- "{\"numerator\":280583613916947,\"denominator\":2500000000000000}"
+-- >>> encode (Lat x)
+-- "0.11223345"
+-- 
+-- With too few decimal places, the encoding will be lossy.
+-- 
+-- >>> decode (encode x) == Just x
+-- True
+-- >>> decode (encode (Lat x)) == Just (Lat x)
+-- False
+-- >>> let Just (Lat y) = decode (encode (Lat x)) in fromRational y
+-- 0.11223345
+--
+-- Similarly for CSV.
+--
+-- >>> :{
+-- instance ToField Lat where
+--     toField = toField . ViaSci
+-- instance FromField Lat where
+--     parseField c = do ViaSci x <- parseField c; return x
+-- :}
+--
+-- >>> Csv.encode [("A", Lat x)]
+-- "A,0.11223345\r\n"
+-- >>> Csv.decode Csv.NoHeader (Csv.encode [("B", Lat x)]) == Right (fromList [("B", Lat x)])
+-- False
+-- >>> Csv.decode Csv.NoHeader (Csv.encode [("C", Lat x)]) == Right (fromList [("C", Lat . fromSci . toSci (DecimalPlaces 8) $ x)])
+-- True
diff --git a/package.dhall b/package.dhall
new file mode 100644
--- /dev/null
+++ b/package.dhall
@@ -0,0 +1,69 @@
+  ./defaults.dhall 
+⫽ { name =
+      "detour-via-sci"
+  , version =
+      "1.0.0"
+  , synopsis =
+      "JSON and CSV encoding for rationals as decimal point numbers."
+  , description =
+      "Lossy JSON and CSV encoding and decoding for newtype rationals via scientific with fixed decimal places."
+  , category =
+      "data, math, numeric, json, csv"
+  , github =
+      "blockscope/flare-timing/detour-via-sci"
+  , homepage =
+      "https://github.com/blockscope/flare-timing/tree/master/detour-via-sci#readme"
+  , library =
+      { dependencies =
+          [ "base >=4.5 && <5"
+          , "newtype"
+          , "scientific"
+          , "aeson"
+          , "cassava"
+          , "template-haskell"
+          , "siggy-chardust"
+          ]
+      , source-dirs =
+          "library"
+      , exposed-modules =
+          [ "Data.Via.Scientific" ]
+      }
+  , tests =
+      { hlint =
+          { dependencies =
+              [ "base"
+              , "hlint"
+              , "newtype"
+              , "scientific"
+              , "aeson"
+              , "cassava"
+              , "template-haskell"
+              , "siggy-chardust"
+              ]
+          , ghc-options =
+              [ "-rtsopts", "-threaded", "-with-rtsopts=-N" ]
+          , main =
+              "HLint.hs"
+          , source-dirs =
+              [ "library", "test-suite-hlint" ]
+          }
+      , doctest =
+          { dependencies =
+              [ "base"
+              , "newtype"
+              , "scientific"
+              , "aeson"
+              , "cassava"
+              , "template-haskell"
+              , "siggy-chardust"
+              , "doctest"
+              ]
+          , ghc-options =
+              [ "-rtsopts", "-threaded", "-with-rtsopts=-N" ]
+          , main =
+              "DocTest.hs"
+          , source-dirs =
+              [ "library", "test-suite-doctest" ]
+          }
+      }
+  }
diff --git a/test-suite-doctest/DocTest.hs b/test-suite-doctest/DocTest.hs
new file mode 100644
--- /dev/null
+++ b/test-suite-doctest/DocTest.hs
@@ -0,0 +1,12 @@
+module Main (main) where
+
+import Test.DocTest (doctest)
+
+arguments :: [String]
+arguments =
+    [ "-isrc"
+    , "library/Data/Via/Scientific.hs"
+    ]
+
+main :: IO ()
+main = doctest arguments
diff --git a/test-suite-hlint/HLint.hs b/test-suite-hlint/HLint.hs
new file mode 100644
--- /dev/null
+++ b/test-suite-hlint/HLint.hs
@@ -0,0 +1,15 @@
+module Main (main) where
+
+import Language.Haskell.HLint (hlint)
+import System.Exit (exitFailure, exitSuccess)
+
+arguments :: [String]
+arguments =
+    [ "library"
+    , "test-suite-hlint"
+    ]
+
+main :: IO ()
+main = do
+    hints <- hlint arguments
+    if null hints then exitSuccess else exitFailure