CODEWITHSUNDEEP
haskellfunctional-programming
Sparkee93
Sparkee93

Reputation: 13

Haskell Beginner problems, list comprehension with single input

I am brand new to haskell and functional programming in general.

How can I create a function that finds all odd numbers less than 200 that are divisible by 3 and 7 using only list comprehension?

this is my code:

oddsDivisible3and7 :: Integer -> Integer -> Integer -> Integer -> [Integer] 
oddsDivisible3and7 xs = [x | x <- [1..xs],x mod 3 == 0 && x mod 7 == 0,x < 200]

and the errors it is throwing:

• Couldn't match expected type ‘(Integer -> Integer -> Integer)
                                -> Integer -> Integer’
              with actual type ‘Integer’  
• The function ‘x’ is applied to two arguments,
  but its type ‘Integer’ has none
  In the first argument of ‘(==)’, namely ‘x mod 3’
  In the first argument of ‘(&&)’, namely ‘x mod 3 == 0’

with another block for the mod 7

I'm not looking for a written function, I just need some guidance.

Upvotes: 1

Views: 395

Answers (1)

developer_hatch
developer_hatch

Reputation: 16224

There are a few type error and a few sintax error, let me show:

oddsDivisible3and7 :: Integral a => a -> [a]
oddsDivisible3and7 n = [x | x <- [1..n],
 x `mod` 3 == 0 && x `mod` 7 == 0 && x < 200 && x `mod` 2 /= 0]

first of all the type should be: Integral a => a -> [a]

Then, you want the divisible by 3, 7 and the odds (not divisible by 2), and all less than 200.

example:

oddsDivisible3and7 500
=> [21,63,105,147,189]

Upvotes: 2

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