When I first started using Rust, I really missed monads. But here’s the thing. Having used lots of monads in Haskell, and read lots of blog posts about monads, I’ve learned that in systems contexts, it’s often best to just have a simple monad stack that just consists of Reader + IO (and Maybe’s and Option’s sprinkled about occasionally). Huge monad transformer stacks often raise more problems than they solve. But Reader + IO is essentially the “default monad stack” of Rust. — Haskell’s Children