Euler19.hs

module Euler19 where
import Control.Monad.List
         

euler19 = length [ (k,j,m,q) | 
                   k <- [19 .. 20]
                 , j <- [0 .. 99]
                 , m <- [1 .. 12]
                 , q <- [1 .. 31]
                 , let n = (zeller k j m q)
                 , not(k==19) || j>0
                 , not(k==20) || j==0
                 , not (m == 9 || m == 4 || m==6 || m==11) || (q<=30)
                 , not ((leapYear (k*100+j)) && m==2) || (q<=29)
                 ,  ((leapYear (k*100+j)) && m==2)  || (q<=28)
                 , n == 1 && q == 1
                 ]
leapYear :: Integer -> Bool
leapYear y 
    | y `mod` 400 ==0 = True
    | y `mod` 100 ==0 = False
    | y `mod` 4   ==0 = True
    | otherwise = False

zeller j k m q 
      | m < 3 = g j (k-1) (m+12) q
      | otherwise  = g j k m q
      where 
        g j k m q  =   (q 
                        + ((((m+1)*26) `div` 10)) 
                        + k  
                        + ((k `div` 4)) 
                        + ((j `div` 4)) 
                        - 2*j) `mod` 7
    
floor' :: (Integral a) => a -> a
floor' = floor . fromIntegral

, not (P) || (Q)ね