Komachi-zan 2013. Run as follows: $ runghc komachi2013gen.hs | runghc komachi2013chk.hs

komachi2013chk.hs

{-# Language TemplateHaskell, QuasiQuotes, FlexibleContexts #-}↲
↲
import Control.Monad↲
import Text.Peggy↲
↲
[peggy|↲
expr :: Double↲
  = expr "+" fact { $1 + $2 }↲
  / expr "-" fact { $1 - $2 }↲
  / fact↲
↲
fact :: Double↲
  = fact "*" number { $1 * $2 }↲
  / number↲
↲
number ::: Double↲
  = [1-9] [0-9]* { read ($1 : $2) }↲
|]↲
↲
main = do↲ 
  inputLines <- getContents↲
  -- print . lines $ inputLines↲
  forM_ (lines inputLines) $ \line -> do↲
    case parseString expr "<stdin>" line of↲
      Right 2013 -> putStrLn line↲
      _ -> return ()↲

komachi2013gen.hs

import Data.Char↲
↲
genexpr n s =↲
  if (n == 10)↲
    then do↲ 
      putStrLn $ reverse s↲
    else do↲ 
      let c = chr $ n + ord '0'↲
      let s1 = c:s↲
      genexpr (n + 1) s1↲ 
      let s2 = c:'-':s↲
      genexpr (n + 1) s2↲ 
      let s3 = c:'+':s↲
      genexpr (n + 1) s3↲ 
      let s4 = c:'*':s↲
      genexpr (n + 1) s4↲ 
↲
main = do↲ 
  genexpr 2 "1"↲