mhug_meetup_26_01_2017.hs

{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE TemplateHaskell #-}

import Control.Lens
import Control.Lens.Operators
import Data.List
import Control.Monad
import Control.Monad.State

vec1 = [1  .. 3]
vec2 = [11 .. 13]

myZipWith op [] [] = []
myZipWith op _ [] = error "dimension mismatch"
myZipWith op [] _ = error "dimension mismatch"
myZipWith op (hL1:tL1) (hL2:tL2) =
  op hL1 hL2 : myZipWith op tL1 tL2

main = do
  print vec1
  print vec2
  print (zipWith (+) vec1 vec2)

data Foo = Foo { _x :: Int
               , _y :: Double
               } deriving (Show)

makeLenses ''Foo

myData = Foo 1 2

foo = myData &~ loop
  where
  loop = forM_ [2..8] $ \t -> do
    x += 5
    x += 6
    q <- use x
    x += 2
    x += t
    y -= 55

primes :: [Integer]
primes             = 2 : 3 : 5 : filter (isPrime) [7..]
isPrime            = not . isNotPrime
isNotPrime x       = any (x `isDivisibleBy`) (asManyAsWeNeed x primes)
asManyAsWeNeed x l = takeWhile (<= lbsqr x) l
lbsqr x            = floor (sqrt (fromIntegral x))
isDivisibleBy a b  = 0 == a `mod` b