jmikkola

mem = {}

def collatz_len(n):
    if n < 2:
        return 1
    if n not in mem:
        chain = 1 + collatz_len(n/2 if n%2 == 0 else 3*n + 1)
        mem[n] = chain
    return mem[n]

jmikkola

def f(k, n):
    '''
    k indistinct bucket,
    n (n > k) balls,
    each bucket must have at least one ball,
    how many ways are there to put n balls in k buckets?
    '''
    if k == 1:
        # Only one way to put things in one bucket
        return 1

jmikkola

import Control.Monad (liftM)
import Data.IORef (IORef, newIORef, modifyIORef', readIORef)
import Data.Map (Map)
import qualified Data.Map as Map

import Control.Monad.Trans.Except (ExceptT, Except, except, runExcept, mapExcept, throwE)
import Control.Monad.IO.Class (liftIO)

data IVal
  = IInt Int

jmikkola

{-# LANGUAGE DeriveFunctor #-}

import Control.Monad.Free

data MThing next
  = MItem String next
  | MEnd
  deriving (Show, Functor)

doThing :: Free MThing ()

jmikkola

data IOOp
  = EndProgram
  | ReadLine (String -> IOOp)
  | WriteLine String IOOp

runOp :: IOOp -> IO ()
runOp EndProgram = return ()
runOp (ReadLine f) = do
  line <- getLine

jmikkola

with open('img.ppm', 'w') as outf:
    outf.write('P6 256 256 255 ')
    for i in xrange(256):
        for j in xrange(256):
            outf.write('%c%c%c' % (i ^ j, i ^ (255 - j), (i+j) % 256))

jmikkola

import re, sys # this file requires python 3
def parse(tokens):
    stack = ([], None)
    for t in tokens:
        if t == '(':
            stack = ([], stack)
        elif t == ')':
            (finished_list, stack) = stack
            stack[0].append(finished_list)
        elif not t.startswith(';;'):

jmikkola

import Control.Concurrent

main = do
  setNumCapabilities 4
  result <- parallelDoWork 38 4
  --result <- doWork 38 4
  putStrLn $ show result

parallelDoWork n m = do
  resultMVars <- mapM (\_ -> forkWork n) [1..m]

jmikkola

Erlang Cheat Sheet

(this is a work in progress)

Running Erlang

Getting the interpreter in ubuntu: sudo apt-get install erlang. To get native compliation capability, also install erlang-base-hipe.

Starting the interpreter: erl. To exit: Ctrl-g then q enter.

jmikkola

import Control.Monad (liftM)
import Control.Monad.Except

type MyMonad = ExceptT String IO

successVal :: MyMonad Int
successVal = return 123

errVal :: MyMonad Int
errVal = throwError "this is an error"