title: What does the dot equals and dot colon syntax mean in Haskell?
body: <p>What does the dot equals (<code>.=</code>) and dot colon (<code>.:</code>) syntax mean in this example taken from the Aeson JSON library?</p>
  
  <pre><code>instance ToJSON Coord where
    toJSON (Coord xV yV) = object [ "x" .= xV,
                                "y" .= yV ]
  
  -- A FromJSON instance allows us to decode a value from JSON.  This
  -- should match the format used by the ToJSON instance.
  
  instance FromJSON Coord where
    parseJSON (Object v) = Coord &lt;$&gt;
                           v .: "x" &lt;*&gt;
                           v .: "y"
    parseJSON _          = empty
  </code></pre>
  
  <p>Full example on Github: <a href="https://github.com/bos/aeson/blob/master/examples/Simplest.hs" rel="noreferrer">https://github.com/bos/aeson/blob/master/examples/Simplest.hs</a></p>