![]() ![]() Let’s start from the end of the list at 5 and follow it up to 1. Result - value of accx after applying flg1 The higher-order library function filter selects every element from a list that satisfies a predicate. filter :: (a -> Bool) -> a -> a Notice here that the filtered value doesn’t create a new array. Here is what a filter looks like according to Haskell’s documentation. Given the following legend: x - element in the listĪccx - value of accumulator at current combinationįlg1 - value of flag at current combination Like maps in Haskell, a filter is also another type of higher-order function that you can employ for your purposes. Description: returns a list constructed from members of a list (the second argument) fulfilling a. All the combinations returned from listA2 are then returned into foldr as the new value of the accumulator acc.īecause filterM is implemented using foldr the accumulated values are used from last to first. ![]() They operate on the values and return a new value. Functions do NOT modify the values that you pass them. In fact, this is a common theme across Haskell. liftA2 is creating a Cartesian product of the flags and the accumulator acc and combining them with supplied function, which prepends the current value of the list x to the accumulator accx if the flag is True or returns the existing accumulator accx if it is False. The filter function does not change the list that you pass it.There are two main expansions happening in the implementation of filterM: Not function signature: Bool -> Bool: This is the signature of the not function given by the official documentation of the Haskell, it returns us the Boolean Value. From reading the type of filter, we know that our. The values passed will be the Cartesian product of and the accumulator of list acc, which is initially ]. Like foldl, foldr takes a function and a base case (what to do when the input list is empty) as arguments. FilterM p = foldr (\x acc -> liftA2 (\flg1 accx -> if flg1 then (x :accx) else accx) (p x) acc) ( pure )Īccx is the accumulator value passed to liftA2. Here we present a robust and efficient Bloom filter implementation in Haskell, and implement a simple bioinformatics application for indexing and matching. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |