I've got a predefined class:I want to use the function 'map' with the class, and so I have to access the [Double]-value. But I do not know how.

## What is the main difference between Free Monoid and Monoid?

Looks like I have a pretty clear understanding what a Monoid is in Haskell, but last time I heard about something called a free monoid.

## Can not use Show even if type implements it

I do not understand why i Show typeclass complains on using a custom type since i already provided an instance for it :

## How do I show more digits of haskell's pi?

I'd like to take more digits of the Prelude pi value.ButIs the pi constant just stored this truncated? Is there an option in show to print to string more digits?

## How to solve this math Function in Haskell?

How can I solve this math Funcion with Haskell? Can anyone help me?Rekursive math FunctionDo I need two recursion? because for this problem in java needs two or three loops.

## How to flatten IO (IO ())?

I'm just learning Haskell and monad transformers and I've found myself with an IO (IO ()) that I'd like to flatten into just IO (). I'm sure that I'm doing something wrong, but can't pinpoint exactly where I'm getting lost.

## Why can't I write the function like this?

I am studying for an "Introduction to Functional Programming" exam. This is one of the problems I am stuck on:

## Why does `and` return True for empty foldable but `or` return False in Haskell? [duplicate]

This question already has an answer here:Is there a reason that would explain whether such results are to be expected? Are they better than being undefined?

## `(a -> b) -> (c -> d)` in Haskell?

This is yet another Haskell-through-category-theory question.Let's take something simple and well-known as an example. fmap? So fmap :: (a -> b) -> f a -> f b, omitting the fact that f is actually a Functor. As far as I understand, (a -> b) -> f a -> f b...

## Why is this unsafeCoerce not unsafe?

Some library use unsafeCoerce to temporarily satisfy constraint:(This example is from reflection package. singletons package also uses this trick.)