hashmap | This package implements a hashmap in Elm | JSON Processing library

I'm working on a request validation feature where I need to check if a certain string value is present in a property that is contained in an object, which is contained as a value of a map entry, that map is a part of an object and finally my request body contains a set of those objects.

To try and make it clearer I will recreate my situation using only parts of code that are important.

Lets say my ClassA is received in request body, it has following properties:

I Generates a checkbox list from the map. Now how to set the value for the key (false / true) and now I can download it in UserConfig so that I can use this value in the rest of the project.

My view:

The following code produces the lifetime errors below despite the fact that the V instance in question is owned.

Got a Map> mapOfMaps variable.

Given a sorted array like [1,2,4,4,4]. Each element in the array should occur exactly same number of times as element. For Example 1 should occur 1 time, 2 should occur 2 times, n should occur n times, After minimum number of moves, the array will be rendered as [1,4,4,4,4]

I have this class:

I was wondering what was the complexity of the replace(Key , Value) for a HashMap is.

My initial thoughts are O(1) since it's O(1) to get the value and I can simply replace the value assigned to the key.

I'm unsure as to if I should take into account collisions that there might be in a large hashmap implemented in java with java.util.

From the bird's view, my question is: Is there a universal mechanism for as-is data serialization in Haskell?

The origin of the problem does not root in Haskell indeed. Once, I tried to serialize a python dictionary where a hash function of objects was quite heavy. I found that in python, the default dictionary serialization does not save the internal structure of the dictionary but just dumps a list of key-value pairs. As a result, the de-serialization process is time-consuming, and there is no way to struggle with it. I was certain that there is a way in Haskell because, at my glance, there should be no problem transferring a pure Haskell type to a byte-stream automatically using BFS or DFS. Surprisingly, but it does not. This problem was discussed here (citation below)

Currently, there is no way to make HashMap serializable without modifying the HashMap library itself. It is not possible to make Data.HashMap an instance of Generic (for use with cereal) using stand-alone deriving as described by @mergeconflict's answer, because Data.HashMap does not export all its constructors (this is a requirement for GHC). So, the only solution left to serialize the HashMap seems to be to use the toList/fromList interface.

I have quite the same problem with Data.Trie bytestring-trie package. Building a trie for my data is heavily time-consuming and I need a mechanism to serialize and de-serialize this tire. However, it looks like the previous case, I see no way how to make Data.Trie an instance of Generic (or, am I wrong)?

So the questions are:

1. Is there some kind of a universal mechanism to project a pure Haskell type to a byte string? If no, is it a fundamental restriction or just a lack of implementations?

2. If no, what is the most painless way to modify the bytestring-trie package to make it the instance of Generic and serialize with Data.Store

I'm fairly new to Java coming from a Python and C# background. I don't know why I am getting a null value for HashMap.getOrDefault() when from my understanding, this method is built in the first place to avoid NullPointer exceptions. The people object is not null, neither is idKey.