I understand that asking “why my code does not work” is not the best question. However, I am asking as I wish to learn more about using monads in Hask ...

I have a computation where I'm inserting values into a Map and then looking them up again. I know that I never use a key before inserting it, but usin ...

This question is a sequel of this thread: https://stackoverflow.com/a/54317095/4400060 I was asking there about carrying STRef in ReaderT's environme ...

The documentation for Data.Vector.unsafeFreeze says: Unsafe[ly] convert a mutable vector to an immutable one without copying. The mutable vector m ...

However, the documentation for STT says: This monad transformer should not be used with monads that can contain multiple answers, like the list mo ...

Using the StateT monad transformer, I can create the type StateT s [] a, which is isomorphic to s -> [(a, s)]. Now I would prefer to use the STT mo ...

Here's the scenario: Given is a C library, with some struct at its core and operations thereon provided by an abundance of C functions. Step 1: Usin ...

I have been learning Haskell for the past month or two, and recently solved this coding problem. The additional challenge was to do the task without e ...

I have written the following code in Haskell using ST monad and it works. My only question is how do I avoid the copy-paste shown in the code below. W ...

The ST monad, originally devised by Launchbury and Peyton Jones, allows Haskell programmers to write imperative code (with mutable variables, arrays, ...

I recently began looking at core libraries on Hackage, and there's a recurring idiom I don't understand. Here's an example from the ST module: In p ...

I'm trying to build a recursive function, which for simplicity's sake, lets say it takes an list and builds an array and a list. Because I need to bot ...

How can I write the following function tt, which has currently type error: I thought that inside runST in tt, state variable s can be threaded into ...

This recent SO question prompted me to write an unsafe and pure emulation of the ST monad in Haskell, a slightly modified version of which you can see ...

I want to implement the Fisher-Yates algorithm (an in-place array shuffle) without side effects by using an STArray for the local mutation effects, an ...

I wrote small program in haskell to count all ocurences of Int values in Tree using State Monad with Vector: But 'update' of immutable Vectors is d ...

I've been working out how to create and use multiple STUArrays in an ST computation. The specific scenarios are: create multiple arrays but return ...

Mutable vectors in Haskell have three element-level mutators: Now I can use these fine -- But what is going on here? What is a PrimMonad? And is ...

I'm having a slight problem implementing a particle based fluid simulation in Haskell for a programming competition. I currently have an array of part ...

I'm reading the paper Typed Logical Variables in Haskell, but I'm failing to understand the details of the ultimate implementation. In particular, the ...