pipes server-client example

rahkana-example.hs

-- Example of using the Rakhana libraries.

-# LANGUAGE NoMonomorphismRestriction #-}

module Foo
where

import Data.Rakhana
import Control.Monad.Trans (liftIO)
import qualified Data.ByteString.Char8 as B

showBytes b = do
  putStr $ "bytes length: " ++ show (B.length b) ++ " |"
  B.putStr b
  putStrLn "|"

myDrive :: Drive IO ()
myDrive = do liftIO $ putStrLn "Hello!"
             b <- driveGet 5
             liftIO $ showBytes b
             driveDiscard 3
             b <- driveGet 4
             liftIO $ showBytes b

example :: IO ()
example = runDrive (fileTape "input") myDrive

server-client.hs

-- This type checks:

import Pipes
import Pipes.Core

server :: Server Int String IO ()
server = undefined

client :: Client Int String IO ()
client = undefined

example = runEffect $ server >>~ const client

server-client2.hs

{-# LANGUAGE RankNTypes, NoMonomorphismRestriction #-}

module Bar where

import Pipes
import Pipes.Core
import Control.Monad.Trans (liftIO)

-- types of Requests:
data Req = Odd Int | Positive Int | Succ Int

-- types of Responses:
data Resp = U | B Bool | I Int

type Answerer m a = Server' Req Resp m a
type Asker    m a = Client' Req Resp m a

serverLoop :: Monad m => Req -> Answerer m a 
serverLoop rq = do
  let r = case rq of
            Odd n      -> B (odd n)
            Positive n -> B (n > 0)
            Succ n     -> I (n+1)
  rq' <- respond r
  serverLoop rq'

asker :: (MonadIO m, Monad m) => Asker m ()
asker = do
  B b <- request (Odd 3)
  liftIO $ putStrLn $ "is 3 odd? -> " ++ show b
  B b <- request (Positive 0)
  liftIO $ putStrLn $ "is 0 positive? -> " ++ show b
  I n <- request (Succ 41)
  liftIO $ putStrLn $ "what comes after 41? -> " ++ show n

startServer = do
  r <- respond undefined
  serverLoop r

example = runEffect $ startServer >>~ (const asker)