Example combining <!> default values and <?> documented fields?

[austinvhuang]

The docs have examples using <?> for documentation and an example using <!> for default values. It's not obvious (to me at least) how to use them together. Could you provide an example of this?

[Gabriella439]

Here is an example of using both:

{-# LANGUAGE DataKinds          #-}
{-# LANGUAGE DeriveGeneric      #-}
{-# LANGUAGE FlexibleInstances  #-}
{-# LANGUAGE OverloadedStrings  #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE TypeOperators      #-}

import Options.Generic

data Example w = Example
    { foo :: w ::: (Int    <?> "Documentation for the foo flag" <!> "1"  )
    , bar :: w ::: (Double <?> "Documentation for the bar flag" <!> "2.0")
    } deriving (Generic)

instance ParseRecord (Example Wrapped)
deriving instance Show (Example Unwrapped)

main = do
    x <- unwrapRecord "Test program"

    print (x :: Example Unwrapped)