int num=1011;
char hexletter[17];
char hex;
hexletter="0123456789ABCDEF";
hex=hexletter[(num/125)+(num-(num/1000)-(num%100))/25+(num-(num/100)-(num%10))/5+(num%10)];

-- Turn an integer into a string
convertToStr :: Int -> Int -> String
-- Regardless of radix, zero is an empty string
convertToStr 0 _ = ""
-- With any other number...
convertToStr n r = convertToStr nextNumber r ++ thisDigitStr
  where
    -- All possible digits
    digits       = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    -- Find the last digit by "mod"ing
    -- the number by the radix
    thisDigit    = n `mod` r
    -- Find the digit in the string which
    -- corresponds to the digit we just calculated
    thisDigitStr = [digits !! thisDigit]
    -- The next time we run the function
    -- we use the number input minus the last digit
    nextNumber   = n `div` r

convertToStr 255 16

convertToStr 255 16
convertToStr 15 16 ++ [digits !! 15]
convertToStr 15 16 ++ "F"
[digits !! 15] ++ "F"
convertToStr 0 16 ++ "F" ++ "F"
"" ++ "F" ++ "F"
"FF"

        int num=1111;
        char hexletter[17]="0123456789ABCDEF";
        char hex;
        hex=hexletter[(num/125)+((num%1000)-(num%100))/25+((num%100)-(num%10))/5+(num%10)];

char hexletter[17]="0123456789ABCDEF";

String hexletter="0123456789ABCDEF";

char[4] theChars = {'a', 'b', 'c', '\0'};