ModValue (雑)

modulo.hs

-- author: Leonardone @ NEETSDKASU

-- modvalue MUST BE PRIME!
modvalue :: Integral a => a
modvalue = 10^9 + 7

(+%),(-%),(*%),(/%) :: Integral a => a -> a -> a
a +% b = (a+b) `mod` modvalue
a -% b = a +% (modvalue - b)
a *% b = (a*b) `mod` modvalue
a /% b = a *% modinv b

modinv v = modpow v (modvalue-2)
modsum xs = foldl1 (+%) xs
modpow _ 0 = 1
modpow v 1 = v
modpow v p | odd p = v *% modpow v (p-1)
           | otherwise = modpow (v*%v) (p`div`2)