module HeavyStuff where

--------------------------------------------------------------------------------
-- * Fibonacci numbers.

fib :: Int -> Int
fib 0 = 0
fib 1 = 1
fib n = fib (n - 1) + fib (n - 2)

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-- * Euler's formula for primes.

euler :: Int -> Int
euler n = sum $ map primes [1 .. n - 1]
  where
    primes :: Int -> Int
    primes n = length $ filter (isRel n) [1 .. n - 1]

    isRel :: Int -> Int -> Bool
    isRel n x = gcd n x == 1

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-- ** Task 1: Just the one.

mFib :: Int
mFib = fib 38

mEuler :: Int
mEuler = euler 5300

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-- ** Task 2: More more more!

mFibs :: [Int]
mFibs = map fib [37,38,39,40]

mEulers :: [Int]
mEulers = map euler [7600, 7600]