Add an example for encoding with a header

examples/csv/encoding-header.expected.csv

@@ -0,0 +1,4 @@
+Bytestring,Text,Int,Double,Text2,Double2,Sum
+Hello,Goodbye,5,5.1,text,0.5,20
+Yes,no,200,-4.5,,22.0,19.3
+a,b,0,0.0,"words ""words"" words",15.0,More words

examples/src/Data/Sv/Example/Encoding.hs

@@ -130,7 +130,7 @@ examples =
   ]
 
 opts :: EncodeOptions
-opts = defaultEncodeOptions & terminalNewline .~ False
+opts = defaultEncodeOptions
 
 main :: IO ()
 main = do

examples/src/Data/Sv/Example/EncodingWithHeader.hs

@@ -0,0 +1,65 @@
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE TemplateHaskell #-}
+
+module Data.Sv.Example.EncodingWithHeader (main) where
+
+import Control.Monad (when)
+import qualified Data.ByteString.Lazy as LBS
+import Data.Semigroup ((<>))
+import System.Exit (exitFailure)
+
+import Data.Sv
+import qualified Data.Sv.Encode as E
+import Data.Sv.Example.Encoding (Example (..), sumEnc, examples, e1,e2,e3,e4,e5,e6,p1,p2)
+
+-- This module demonstrates encoding with a header.
+--
+-- It is worth looking at Encoding.hs before this module, as this module
+-- imports definitions from that module.
+--
+-- EncodingWithHeader.hs focuses on encoding with a header, whereas Encode.hs
+-- is mostly about showing off different ways to define an encoder.
+
+expectedFile :: FilePath
+expectedFile = "csv/encoding-header.expected.csv"
+
+opts :: EncodeOptions
+opts = defaultEncodeOptions
+
+-- Here we build our encoder, attaching a name to each column
+exampleEnc :: NameEncode Example
+exampleEnc =
+      "Bytestring" =: E.encodeOf e1 E.byteString
+  <>  "Text" =: E.encodeOf e2 E.text
+  <>  "Int" =: E.encodeOf e3 E.int
+  <>  "Double" =: E.encodeOf e4 E.double
+  -- Notice that we have had to inline the definition of productEnc to
+  -- attach a name to each component of it.
+  --
+  -- The lesson is that if one wants encoding with column names, this should
+  -- be built-in as you go. It can be tricky to attach names to the right
+  -- places after the fact.
+  -- This could also be avoided by not using ADTs within the data
+  -- type to be encoded.
+  <>  "Text2" =: E.encodeOf (e5.p1) E.text
+  <>  "Double2" =: E.encodeOf (e5.p2) E.double
+  <>  "Sum" =: E.encodeOf e6 sumEnc
+
+
+
+main :: IO ()
+main = do
+  expected <- LBS.readFile expectedFile
+  putStrLn "Data to encode:"
+  print examples
+  putStrLn "Expected"
+  LBS.putStr expected
+  putStrLn ""
+  putStrLn "Encoded:"
+  let encoded = encodeNamed exampleEnc opts examples
+  LBS.putStr encoded
+  putStrLn ""
+
+  -- validation
+  when (expected /= encoded)
+    (putStrLn "expected /= encoded" *> exitFailure)

examples/sv-examples.cabal

@@ -26,6 +26,7 @@ tested-with:         GHC == 7.10.3
 library
   exposed-modules:     Data.Sv.Example.Columnar
                        , Data.Sv.Example.Encoding
+                       , Data.Sv.Example.EncodingWithHeader
                        , Data.Sv.Example.Numbers
                        , Data.Sv.Example.Ragged
                        , Data.Sv.Example.Species

examples/test/test.hs

@@ -1,5 +1,6 @@
 import qualified Data.Sv.Example.Columnar as Columnar
 import qualified Data.Sv.Example.Encoding as Encoding
+import qualified Data.Sv.Example.EncodingWithHeader as EncodingWithHeader
 import qualified Data.Sv.Example.Numbers as Numbers
 import qualified Data.Sv.Example.Ragged as Ragged
 import qualified Data.Sv.Example.Species as Species
@@ -9,6 +10,7 @@ main :: IO ()
 main = do
   Columnar.main
   Encoding.main
+  EncodingWithHeader.main
   Numbers.main
   Ragged.main
   Species.main

src/Data/Sv.hs

@@ -32,6 +32,7 @@ module Data.Sv (
   , decodeMay
   , decodeEither
   , decodeEither'
+  , (.:)
   , (>>==)
   , (==<<)
   , module Data.Sv.Parse
@@ -48,6 +49,7 @@ module Data.Sv (
   , encodeNamedToHandle
   , encodeNamedBuilder
   , encodeRow
+  , (=:)
   , module Data.Sv.Encode.Type
   , module Data.Sv.Encode.Options