MgaMPKAy

Channels Are Not Enough

... or Why Pipelining Is Not That Easy

Golang Concurrency Patterns for brave and smart.

By @kachayev

Intro

MgaMPKAy

{-# LANGUAGE OverloadedStrings #-}

import Parser
import Types
import Network.HTTP.Client
import Control.Applicative
import Control.Monad.Trans (liftIO)
import Database.InfluxDB

main = do

MgaMPKAy

import Control.Concurrent
import Control.Monad
import Data.IORef

main = do
    c   <- newIORef (0::Int)
    arr <- newIORef []

    replicateM_ 100 $ forkIO $ thread c

MgaMPKAy

import Options.Applicative
import Data.Monoid

type PackageDB = String
type Package   = String
type Dir       = String
type Archive   = String

data Options = Options [PackageDB] Command deriving (Show)

MgaMPKAy

import Data.Monoid
import Data.Maybe

fizzBuzzWhizz (x, y, z) a =
    fromJust $ getFirst $ mconcat $ map First
        [ x `contains` a
        , fizz a x <> buzz a y <> whizz a z
        , Just $ show a
        ]
  where

MgaMPKAy

{-# LANGUAGE ViewPatterns #-}
{-# LANGUAGE PatternSynonyms #-}
import System.Environment
import Data.Ratio
import Control.Applicative ((<$>))

viewRatio x = (numerator x, denominator x)
pattern p :% q <- (viewRatio -> (p, q))

main = do

MgaMPKAy

{-# LANGUAGE BangPatterns #-}
module NQueens where

import Data.Bits
import Control.Parallel

queue n = queensHelper (1 `shiftL` n - 1) 0 0 0

queensHelper :: Int -> Int -> Int -> Int -> Int
queensHelper !allOnes !leftDiag !columns !rightDiags =

MgaMPKAy

{-# LANGUAGE ScopedTypeVariables #-}
module Sudoku where

import Data.SBV
import Control.Monad (zipWithM_)

sudoku game = do
    vs :: [SWord8] <- mkExistVars 81
    zipWithM_ setVar game vs
    mapM_ (\x -> constrain $ x .>= 1 &&& x .<= 9) vs

MgaMPKAy

{-# LANGUAGE ForeignFunctionInterface #-}
import Foreign
import Foreign.C

data WhiteDB
data Record

foreign import ccall "wg_attach_database" c_wg_attach_database  :: CString -> CInt -> IO (Ptr WhiteDB)
foreign import ccall "wg_detach_database" c_wg_detach_database :: Ptr WhiteDB -> IO CInt

MgaMPKAy

{-# LANGUAGE RecordWildCards #-}

-- 1. Without lenses (and state monad), even a simple flat record becomes clumsy

import System.Random
import System.IO
import Control.Applicative ((<$>))
import Control.Monad (when)
import Text.Read (readMaybe)
import Data.Char (toLower)