ldunn

let gridArray = 
    let arr = (Array2D.init 20 20 (fun i j -> 0))
    for i in [0..(grid.Split '\n').Length-1] do
        for j in [0..((grid.Split '\n').[0].Split ' ').Length-1] do
            arr.[i,j] <- int ((grid.Split '\n').[i].Split ' ').[j]
    arr

ldunn

(* Project Euler Problem 9 
A Pythagorean triplet is a set of three natural numbers, a < b < c, for which,
a2 + b2 = c2

For example, 32 + 42 = 9 + 16 = 25 = 52.

There exists exactly one Pythagorean triplet for which a + b + c = 1000.
Find the product abc.
*)

ldunn

let charToInt x = int (string x)
let number = "73167176531330624919225119674426574742355349194934969835203127745063262395783180169848018694788518438586156078911294949545950173795833195285320880551112540698747158523863050715693290963295227443043557668966489504452445231617318564030987111217223831136222989342338030813533627661428280644448664523874930358907296290491560440772390713810515859307960866701724271218839987979087922749219016997208880937766572733300105336788122023542180975125454059475224352584907711670556013604839586446706324415722155397536978179778461740649551492908625693219784686224828397224137565705605749026140797296865241453510047482166370484403199890008895243450658541227588666881164271714799244429282308634656748139191231628245861786645835912456652947654568284891288314260769004224219022671055626321111109370544217506941658960408071984038509624554443629812309878799272442849091888458015616609791913387549920052406368991256071760605886116467109405077541002256983155200055935729725716362695618826704282524836

ldunn

let generatePairs xs ys = 
    let pairs = ref []
    for i in xs do
        for j in ys do
            if (List.filter (fun y -> ((y = [i;j]) || y = [j;i])) !pairs = []) then
                printfn "%A" [i;j]
                pairs := [i;j] :: !pairs 

ldunn

let euler4 = 
    let largestPalindrome = ref 0
    for i in 100..999 do
        for j in 100..999 do
            if pairMakesPalindrome i j && i*j > !largestPalindrome then
                largestPalindrome := i*j
    !largestPalindrome

ldunn

let rec primesIn (ns: int list) (x: int) =     
    let newList = 
        (List.choose (fun y -> 
            match y with
                | y when (y % x = 0) -> None
                | _ -> Some y) ns)
    if newList.[0]*newList.[0] <= newList.[newList.Length-1] then
        x :: primesIn newList newList.[0]
    else x :: newList

ldunn

let rec primesIn (ns: int list) (x: int) =      
    let newList = 
        (x :: ((List.choose (fun y -> 
        match y with
        | y when (y % x <> 0) -> Some y
        | _ -> None) ns).Tail))
    if newList.[0]*newList.[1] <> newList.[newList.Length-1] then
        primesIn newList.Tail newList.[1]
    else ns

ldunn

let square x:float = x**2
let numbers = [1.0 .. 100.0]
let sum_squares = List.reduce (+) (List.map (square) numbers)
let square_sum = square (List.reduce (+) numbers)

ldunn

[<Measure>] type kg
[<Measure>] type m
[<Measure>] type s
let gravityOnEarth = 9.81<m/s^2>
let heightOfTowerOfPisa = 55.86<m>
let speedOfImpact = sqrt(2.0 * gravityOnEarth * heightOfTowerOfPisa)

ldunn

let rec dividesIntoAllUpTo (n: int) (d: int) =
    match d with 
    | 1 -> true
    | _ -> (n % d = 0) && (dividesIntoAllUpTo n (d - 1))

let matchesCriteria n = 
    dividesIntoAllUpTo n 20

let main = 
    let current_num = ref 20