chore: add example to README

* misc: add example file

* misc: add example

* misc: add pretty print to error bundle of example

* misc: add example explanation to README

Author: cptrodolfox

README.md

@@ -61,6 +61,27 @@ To pretty print a error message use the `parseErrorPretty` function from
 This should be enough to start using the package, please consult Haddocks
 for detailed per-function documentation.
 
+## Example
+
+To check an example using `cassava-megaparsec` check the code in the `example` directory.
+
+Given the following type:
+```haskell
+data Test = Test {a :: Char, b :: Char, c :: Char} deriving (Eq, Show, Generic)
+```
+And, the following csv file:
+```text
+a,ba,c
+```
+We get the following error:
+```
+example.csv:1:7:
+  |
+1 | a,ba,c
+  |       ^
+conversion error: expected Char, got "ba"
+```
+
 ## Contributors ✨
 
 Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/docs/en/emoji-key)):

cassava-megaparsec.cabal

@@ -55,6 +55,19 @@ library
                       -Wnoncanonical-monadfail-instances
   default-language:   Haskell2010
 
+executable cassava-megaparsec-example
+  main-is:            Main.hs
+  other-modules:      Paths_cassava_megaparsec
+  hs-source-dirs:     example
+  ghc-options:        -Wall -threaded -rtsopts -with-rtsopts=-N
+  build-depends:      base
+                    , cassava
+                    , cassava-megaparsec
+                    , text
+                    , vector
+                    , megaparsec
+  default-language:   Haskell2010
+
 test-suite tests
   main-is:            Spec.hs
   hs-source-dirs:     tests

example/Main.hs

@@ -0,0 +1,21 @@
+{-# LANGUAGE DeriveGeneric #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE TypeApplications #-}
+
+module Main where
+
+import Data.Csv (FromRecord, HasHeader (NoHeader))
+import Data.Csv.Parser.Megaparsec (decode)
+import GHC.Generics (Generic)
+import Text.Megaparsec.Error (errorBundlePretty)
+
+data Test = Test {a :: Char, b :: Char, c :: Char} deriving (Eq, Show, Generic)
+
+instance FromRecord Test
+
+main :: IO ()
+main = do
+  let res = decode @Test NoHeader "example.csv" "a,ba,c\n"
+  case res of
+    Left errorBundle -> putStrLn $ errorBundlePretty errorBundle
+    Right value -> print value