CODEWITHSUNDEEP
haskellfunctional-programming
galliwuzz
galliwuzz

Reputation: 369

Creating filter conditions based on list elements

I'm interested in creating a filter, whose conditions depend on an input list. Specifically, I want to define the filter such that it checks whether a number is divisible by any number in my input list. So for a single element that would be:

my_filter a = filter (\x -> x `mod` a == 0)

basically I want to extend this such that if I have an input list, it would do the following:

my_filter [a,b] = filter (\x -> x `mod` a == 0 || x `mod` b == 0)

How can I define this filter recursively, such that each element of the list creates a new condition?

Upvotes: 1

Views: 301

Answers (1)

bheklilr
bheklilr

Reputation: 54078

What you're looking for is the or function:

my_filter divisors = filter (\x -> or $ map ((0 ==) . (x `mod`)) divisors)

If you wanted to filter where all the values were divisors then you just have to change or to and.

Another way to do it would be

my_filter divisors = filter (\x -> any (== 0) $ map (x `mod`) divisors)

These are equivalent functions, just a little different style.

Upvotes: 3

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