f#

// Ex.1

let convertStringToWords s =
    List.foldBack (fun c acc -> if c = ' ' then [] :: acc else [c :: acc.[0]] @ acc.[1..acc.Length-1]) [for ch in s -> ch] [[]]

let printWordsToLines lineLength (ws:char list list) =
    if ws |> List.map (fun w -> w.Length) |> List.max > lineLength then
        failwith "Can not fit"
    let rec wordsToLines (ws:char list list) offset =
        match ws with
        | [] -> []
        | head::tail -> if head.Length + offset < lineLength
                        then head @ [' '] @ wordsToLines tail (offset+head.Length+1)
                        else ['\n'] @ head @ [' '] @ wordsToLines tail (head.Length+1)
    wordsToLines ws 0

//Test
convertStringToWords "Functional programming Fsharp" |> printWordsToLines 20
(*Prints ['F'; 'u'; 'n'; 'c'; 't'; 'i'; 'o'; 'n'; 'a'; 'l'; ' '; '\010'; 'p'; 'r';
   'o'; 'g'; 'r'; 'a'; 'm'; 'm'; 'i'; 'n'; 'g'; ' '; 'F'; 's'; 'h'; 'a'; 'r';
   'p'; ' ']*)

convertStringToWords "Functional programming Fsharp" |> printWordsToLines 8
//Shows an error - longest word is longer then 8



//Ex.2

let maximumWordsOnLine s =
    let splitString s del =
        List.foldBack (fun c acc -> if c = del then [] :: acc else [c :: acc.[0]] @ acc.[1..acc.Length-1]) [for ch in s -> ch] [[]]
    splitString s '\n' |> List.map (fun line -> (splitString line ' ').Length) |> List.max

//Test
maximumWordsOnLine "one two three\none two three four\none\none two\none two three four five\none"
//Returns 5


//Ex.3

let countNumOfVowels s =
     let countVovel v =
        List.fold (fun acc c -> acc + (if List.contains c [v; System.Char.ToUpper v] then 1 else 0)) 0 [for ch in s -> ch]
     (countVovel 'a', countVovel 'e', countVovel 'i', countVovel 'o', countVovel 'u')

//Test
countNumOfVowels "paradigm"
//returns (2, 0, 1, 0, 0)