Haskell程序：检查输入数字是否为Neon数

-- function declaration for sumDigit function
sumDigit :: Int->Int

-- function definition for base condition
sumDigit 0 = 0

-- function definition for all other cases
sumDigit num = mod num 10 + sumDigit (div num 10)

-- function declaration for isNeon function
isNeon :: Int->Bool

-- function definition for isNeon function
isNeon num = num == (sumDigit (num*num))
-- main function

main = do
-- declaring and populating variable with a number
let num = 9
-- invoking the isNeon function and printing the result
print (isNeon 9)

-- function declaration and definition for sumDigit function
sumDigit :: Int->Int
sumDigit 0 = 0
sumDigit num = mod num 10 + sumDigit (div num 10)

-- Function declaration and definition for isNeon function
isNeon :: Int->Bool
isNeon num = num == (sumDigit (num*num))

main = do
-- declaring and initializing upper and lower bounds with values
   let lower = 1
   let upper = 100
-- list comprehension to generate Neon numbers in a range
   let list = [x | x <- [lower..upper], isNeon x]
   print (list)

-- function declaration for sumDigit function
sumDigit :: Int->Int
-- function definition for sumDigit function
sumDigit 0 = 0
sumDigit num = mod num 10 + sumDigit (div num 10)

-- function declaration and definition for isNeon function
isNeon :: Int->Bool
isNeon num = num == (sumDigit (num*num))

-- function declaration for generateNeon function
generateNeon :: Int->Int->[Int]
-- function definition for generateNeon function
generateNeon lower upper = if (upper<lower)
                              then []
                              else if(isNeon upper)
                              then generateNeon lower (upper-1) ++ [upper]
                              else generateNeon lower (upper-1)
main = do
-- declaring and initializing variable for lower and upper bounds
   let lower = 1
   let upper = 100
   print (generateNeon lower upper)