Add main functions to any that were missing

src/projectEuler/question13.hs

@@ -221,4 +221,6 @@ ans :: [Integer]
 ans = take 10 $ reverse . digits $ sum oneHundredFiftyDigitNumbers
 
 main :: IO ()
-main = print ans
+main = do
+  print ans
+  print (sum oneHundredFiftyDigitNumbers)

src/projectEuler/question5.hs

@@ -63,3 +63,5 @@ test = map (filter . multipleOf) [1..10]
 
 -- lol
 solve = foldl1 lcm [1..20]
+
+main = print solve

src/projectEuler/question6.hs

@@ -13,16 +13,29 @@ Find the difference between the sum of the squares
   of the first one hundred natural numbers
   and the square of the sum.
 -}
-upperRange = 100
+upperRange :: Integer
+upperRange = 1_000_000
+
+square :: Num a => a -> a
 square n = n^2
+
+squares :: [Integer]
 squares = map square [1..upperRange]
+
+sum' :: [Integer] -> Integer
 sum' = go 0
   where
     go acc []     = acc
     go acc (x:xs) = go (acc+x) xs
 
-sumOfSquares = sum' squares
+sumOfSquares :: Integer
+sumOfSquares = sum squares
 
-squareOfTheSum = (sum [1..upperRange])^2
+squareOfTheSum :: Integer
+squareOfTheSum = sum [1..upperRange] ^2
 
+solution :: Integer
 solution = squareOfTheSum - sumOfSquares
+
+main :: IO ()
+main = print solution

src/projectEuler/question7.hs

@@ -1,6 +1,9 @@
 -- https://projecteuler.net/problem=7
 -- Find the 10_001 prime number
 
+-- import           Data.Numbers.Primes (primes)
+import           Math.NumberTheory.Primes (primes)
+
 primes1 :: [Integer]
 primes1 = 2:3:prs
   where
@@ -30,3 +33,8 @@ primes2 = 2:([3..] `minus` composites)
 primes3 = sieve [2..]
   where
     sieve (p : xs) = p : sieve [x | x <- xs, x `mod` p > 0]
+
+main :: IO ()
+main = print $ "Arithmoi - Math.NumberTheory.Primes: " <> show ans
+
+ans = primes !! 10_000_000

src/projectEuler/question8.hs

@@ -28,6 +28,7 @@ What is the value of this product?
 module Main where
 
 import           Data.Char       (ord)
+import           Data.Foldable   (maximumBy)
 import           Data.List       (sort)
 import           Data.List.Split (splitOn)
 
@@ -46,9 +47,16 @@ digits = go []
 main :: IO ()
 main = print ans
 
-ans :: [[Integer]]
-ans = (windowsOf 13 . digits) thousandDigitNum
--- "9878799272442"
+ans :: ([Integer], Integer)
+ans = (l, p)
+  where
+    l = maximumBy c $ (windowsOf 13 . digits) thousandDigitNum
+    p = product l
+    c a b
+      | product a > product b = GT
+      | product a < product b = LT
+      | otherwise = EQ
+-- "([5,5,7,6,6,8,9,6,6,4,8,9,5],23514624000)"
 
 -- what dose it mean to have the greatest product in adjacent digits?
 --  why ask it like that???

src/projectEuler/question9.hs

@@ -17,14 +17,39 @@ Find the product `abc`.
 -}
 
 main :: IO ()
-main = print answer
+main = do
+  print answer
+  print (product answer)
 
-answer :: String
-answer = "I dunno"
+-- head $ [(a,b,c) | a <- [1..limit], b <- [a+1..limit], c <- [limit - a - b], a < b, b < c, a^2 + b^2 == c^2]
+answer :: [Integer]
+answer = head $
+  [ [a, b, c] |
+    a <- [1 .. limit],
+    b <- [a + 1 .. limit],
+    c <- [limit - a - b],
+    b < c,
+    a ^ 2 + b ^ 2 == c ^ 2]
+  where limit = 1000
+
+limit = 1000
+version1 =   [ [a, b, c] |
+    a <- [1 .. limit],
+    b <- [a + 1 .. limit],
+    c <- [limit - a - b],
+    b < c,
+    a ^ 2 + b ^ 2 == c ^ 2]
+
+version2 =   [ [a, b, c] |
+    a <- [1 .. limit],
+    b <- [a + 1 .. limit],
+    c <- [limit - a - b],
+    b < c,
+    a ^ 2 + b ^ 2 == c ^ 2]
 
 
 solve :: Integer -> [(Integer, Integer, Integer)]
-solve x = takeWhile (\(a,b,c) -> a + b + c <= 1000) $ primitiveTriplesUnder x
+solve x = takeWhile (\(a,b,c) -> a + b + c == 1000) $ primitiveTriplesUnder x
 
 euclid'sFormula :: Num c => (c, c) -> (c, c, c)
 euclid'sFormula (m, n) = (a,b,c)
@@ -87,19 +112,19 @@ ans' limit = [(a, b, c)
               , b < c
              ]
 
-{- 
+{-
  - Solution to Project Euler problem 9
  - Copyright (c) Project Nayuki. All rights reserved.
- - 
+ -
  - https://www.nayuki.io/page/project-euler-solutions
  - https://github.com/nayuki/Project-Euler-solutions
  -}
 
 
--- Computers are fast, so we can implement a brute-force search to directly solve the problem.
-perim = 1000
-main = putStrLn (show ans)
-ans = head [a * b * (perim - a - b) | a <- [1..perim], b <- [a+1..perim], isIntegerRightTriangle a b]
-isIntegerRightTriangle a b = a < b && b < c
-	&& a * a + b * b == c * c
-	where c = perim - a - b
+-- -- Computers are fast, so we can implement a brute-force search to directly solve the problem.
+-- perim = 1000
+-- main = putStrLn (show ans)
+-- ans = head [a * b * (perim - a - b) | a <- [1..perim], b <- [a+1..perim], isIntegerRightTriangle a b]
+-- isIntegerRightTriangle a b = a < b && b < c
+-- 	&& a * a + b * b == c * c
+-- 	where c = perim - a - b