pascal.elm

module Main exposing (main)

import Html exposing (Html)

numberRows = 5

generate : (a -> a) -> a -> Int -> List a
generate f seed n = 
    if n <= 0 then 
        [f seed] 
    else 
        f seed :: generate f (f seed) (n - 1)


pairwise = 
    List.scanl (\x acc -> (Tuple.second acc, x)) (1, 1)
    >> List.drop 2

pascal = 
    pairwise 
    >> List.map (\(x,y) -> x + y) >> (\l -> [1] ++ l) >> (\l -> l ++ [1])

main : Html msg
main =
    generate pascal [1, 1] numberRows
    |> List.map (String.join "     " << List.map toString)
    |> List.map (\row -> Html.div [] [ Html.text row ])
    |> Html.div []