Haskell-cafe thread on Feb 19 2014

.gitignore

dist
*~
\#*

h.cabal

-- Initial h.cabal generated by cabal init.  For further documentation, see
--  http://haskell.org/cabal/users-guide/

name:                h
version:             0.1.0.0
-- synopsis:
-- description:
-- license:
author:              Gregory Collins
maintainer:          greg@gregorycollins.net
-- copyright:
-- category:
build-type:          Simple
-- extra-source-files:
cabal-version:       >=1.10

executable h1
  main-is: h1.hs
  ghc-options: -Wall -fwarn-tabs -funbox-strict-fields -O2 -fno-warn-unused-do-bind -rtsopts
  build-depends:       base >=4.5 && <4.6,
                       bytestring
  default-language:    Haskell2010

executable h2
  main-is: h2.hs
  ghc-options: -Wall -fwarn-tabs -funbox-strict-fields -O2 -fno-warn-unused-do-bind -rtsopts
  build-depends:       base >=4.5 && <4.6,
                       bytestring,
                       blaze-builder,
                       io-streams
  default-language:    Haskell2010

executable h3
  main-is: h3.hs
  ghc-options: -Wall -fwarn-tabs -funbox-strict-fields -O2 -fno-warn-unused-do-bind -rtsopts
  build-depends:       base >=4.5 && <4.6,
                       bytestring,
                       blaze-builder,
                       io-streams
  default-language:    Haskell2010

h1.hs

module Main where

import qualified Data.ByteString    as BS
import           System.Environment

import           Data.Word

only012 :: Word64 -> Bool
only012 0 = True
only012 n = (q < 3) && only012 p
  where (p,q) = n `divMod` 10

go :: Word64 -> IO ()
go 0 = return ()
go n = if only012 n
       then (BS.putStr $ BS.pack ([1] :: [Word8])) >> go (n-1)
       else (BS.putStr $ BS.pack ([0] :: [Word8])) >> go (n-1)

main = do
  [d] <- map read `fmap` getArgs
  go d

h2.hs

{-# LANGUAGE BangPatterns #-}

module Main where

import           Blaze.ByteString.Builder                 as Blaze
import           Blaze.ByteString.Builder.Internal.Buffer as Blaze
import qualified Data.ByteString                          as BS
import           System.Environment
import qualified System.IO.Streams                        as Streams

import           Data.Word

only012 :: Word64 -> Bool
only012 0 = True
only012 n = (q < 3) && only012 p
  where (!p,!q) = n `divMod` 10

go :: Word64 -> IO ()
go i = do
    buf <- Blaze.allocBuffer 4096
    os <- Streams.unsafeBuilderStream (return buf) Streams.stdout
    f os i
  where
    f os i = g i
      where
        g 0 = return ()
        g n = do
            let !c = if only012 n then 1 else (0::Word8)
            Streams.write (Just $! Blaze.fromWord8 c) os
            g (n-1)

main = do
  [d] <- map read `fmap` getArgs
  go d

h3.hs

{-# LANGUAGE BangPatterns #-}
module Main where

import qualified Data.ByteString    as BS
import           System.Environment

import           Data.Word

only012 :: Word64 -> Bool
only012 0 = True
only012 n = (q < 3) && only012 p
  where (!p,!q) = n `divMod` 10

go :: Word64 -> IO ()
go 0 = return ()
go n = if only012 n
       then (BS.putStr $ BS.pack ([1] :: [Word8])) >> go (n-1)
       else (BS.putStr $ BS.pack ([0] :: [Word8])) >> go (n-1)

main = do
  [d] <- map read `fmap` getArgs
  go d

Setup.hs

import Distribution.Simple
main = defaultMain