Each of the functions in this module is a monadic request modifier, using the ReqMod type. Most of them do not have any side effects; however, the consistent use of Monad allows for easy chaining with bind (>>=) or Kleisli composition (>=>).

Example

The example that inspired this package is modifying the Request from parseUrl:

  parseUrl "http://httpbin.org/post"
    >>= setMethod POST
    >>= setBodyLBS "hello"

Suppose I want to reuse the URL post request but not the body. I can define a function for just that part:

  let httpbinPost :: MonadThrow m => m Request
      httpbinPost = parseUrl "http://httpbin.org/post" >>= setMethod POST

Alternative formulations of the above, without using request modifiers, are:

  parseUrl "http://httpbin.org/post"
    >>= req -> return $ req
      { method = renderStdMethod POST
      , requestBody = RequestBodyLBS "hello"
      }

and

  let httpbinPost :: MonadThrow m => m Request
      httpbinPost = do req <- parseUrl "http://httpbin.org/post"
                       return $ req { method = renderStdMethod POST }

Benefits

The main benefits of monadic request modifiers are:

• composability,
• conciseness, and
• allowing an arbitrary combination of Monads.

Naming Scheme

The naming scheme used for functions in this module is:

• set - Set a value, overriding any existing value.
• add - Append a value to the end of a list and do not override any existing values.
• BS - Use a strict ByteString as a parameter.
• LBS - Use a lazy ByteString as a parameter.