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 monad transformer instead, as I would like to hav...

The ST monad, originally devised by Launchbury and Peyton Jones, allows Haskell programmers to write imperative code (with mutable variables, arrays, etc.) while obtaining a pure interface to that ...

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: instance Monad (ST s) where {-# INLINE (>>=) #...

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 below: {-# LANGUAGE DeriveFunctor, Generalize...

I am trying to work out a data structure for the following situation. Graph Structure I plan to have a graph of nodes with un-weighted, directed edges: Graph = [Node] Each node has: Some TBD i...

I wrote small program in haskell to count all ocurences of Int values in Tree using State Monad with Vector: import Data.Vector import Control.Monad.State import Control.Monad.Identity data Tree ...

Mutable vectors in Haskell have three element-level mutators: read :: PrimMonad m => MVector (PrimState m) a -> Int -> m a write :: PrimMonad m => MVector (PrimState m) a -> Int -&g...

I have some code that currently uses a ST monad for evaluation. I like not putting IO everywhere because the runST method produces a pure result, and indicates that such result is safe to call (ver...