# Solved: how to delete duplicate element in list

As a developer with expertise in Haskell programming, managing data efficiently forms the backbone of quality software development. One common form of data processed in programming is lists. However, a critical issue that often arises in day-to-day programming activities, is dealing with duplicate elements within a list. Today, I will discuss how to solve this issue in Haskell.

Haskell additionally provides a functional programming paradigm and a high level of abstraction, which offers a unique perspective and approach towards resolving various issues in software development, including the removal of duplicate elements in a list.

Now, let’s narrow our focus to the process of eliminating duplicate elements in a list using Haskell.

```removeDuplicates :: (Ord a) => [a] -> [a]
removeDuplicates = foldl (seen x -> if x `elem` seen
then seen
else seen ++ [x]) []
```

The highlighted code removes duplicate elements from a list in Haskell using the `foldl` function and List comprehension. Notably, this function works on lists containing elements of any orderable type. The foldl function traverses the list from left to right and incrementally builds up a result, which in our case, is a list void of any duplicate elements.

The `foldl` function forms an integral part of the proposed Haskell solution. This function is mainly used to reduce a list of elements into a single output, based on a binary operation. This binary operation involves combining the elements of the list with an initial accumulator value. In the above code, the binary operation we’re employing uses a lambda function, wherein `seen` represents the accumulator and `x` the current value.

By building such a list progressively using the foldl function, we are systematically evaluating whether each element already exists in the “seen” list. If the element does exist, we ignore it. Otherwise, we add it to the “seen” list. This technique helps us to generate a list that is rid of duplicate elements.

## Haskell’s List Comprehension Function Explained

Another salient function in the provided Haskell code is the `elem` function within the List comprehension part. The `elem` function, in Haskell, checks if an item belongs to a given list. Here we are using this function collaboratively with list comprehension to carry out a check before adding current value `x` to the `seen` list.

We only append `x` to the `seen` list if `x` is not already part of `seen`. As such, by the end of the fold, the `seen` list will include all the elements from the original list, but with no duplicate entries.

In conclusion, Haskell’s identify and remove duplicate elements in a list issue can be elegantly resolved using language built-in features and specific functions. These include foldl for list reduction and the `elem` function with list comprehension for ensuring a list minus the duplicate entries. By understanding and familiarly with key features and functions in Haskell, one can navigate such common programming issues with much ease and fluidity.

Though this may seem a challenging concept initially, consistently working with Haskell’s foldl and comprehension features will enable the easy creation of neat solutions for complex problems.

Similarly, in the scope of fashion, clean and well-structured styles add charm to the overall look, just like well-structured code that makes programs more efficient and easy to understand. Keeping in pace with the ongoing trends and making the right combination of outfits, colors, and styles, is just like keeping up with the current libraries and functions in development for more efficient coding.

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