Haskell: Transformers vs Monads

What are the main differences between transformers and monads in Haskell?

In Haskell, monads are a type class that represents computations as a series of steps, while transformers are used to combine multiple monads into a single monadic structure. Monads provide a way to handle side effects, while transformers allow you to stack monads.

Can you give me an example of how to use a transformer with a monad?

Sure! For example, you can use the MaybeT transformer to combine the Maybe monad with another monad, like IO. This allows you to perform IO operations that can also fail.

Why would I use transformers instead of just using monads?

Transformers allow for more flexibility and composability. By stacking monads, you can create complex behaviors without having to define a new monad for every combination of effects.

Are there any performance considerations when using transformers?

Yes, using transformers can introduce some overhead due to additional layers of abstraction. However, the trade-off is often worth it for the increased modularity and code reuse.