I was watching this Computerphile video: "What is a Monad?" What is a Monad? - Computerphile - YouTube thinking that Computerphile were likely to be able to explain what is a monad in a simple enough way for normal people to understand. The explanation revolves around creating as simple expression …

Maybe is just an example of a monad. A monad is not a concrete type but a concept / an abstraction. In Rust, Monad would be a trait. However afaik Rust traits are not yet able to represent a monad. Option in Rust is roughly the same as Maybe in Haskell. In a way, Option is already a monad, it's ju…

Monad is a pattern that generalizes behavior, not a specific type. My hubris demands me attempt to summarize the abstraction tower: A functor is a context you can map operations over. So you can turn a function T -> U into a function List<T> -> List<U> or a Option<T> -> Option<U> or a BinaryTree<T> …

Off-topic, but safe_div can be written as fn safe_div(a: Option<i32>, b: Option<i32>) -> Option<i32> { a?.checked_div(b?) } ( playground ) which is simpler IMO.

Carefully read this page. Understand that "do notation" is essentially just traditional imperative code, and that the key property of imperative code is that state is implicitly transferred from one command to the next. The thing that makes Monads a significant development in PL theory and computer …

A monad is a type that looks like a collection and has a flat_map function. A Vec<T> is a monad. An Option<T> is a monad (it's a collection with zero or one elements) and its flat_map is called and_then . A Future is a monad (it's a collection with exactly one element), although you have to squint as…

I forget who said it, but I read an article (or maybe it was a conference talk?) which talked about how Rust will typically approach monads... The Monads pattern let you abstract over something by phrasing the particular concept as a series of transformations. For example, Option<T> lets you abstra…

I agree with this characterization. However it just raises the question for me why Rust didn't just add the type infrastructure (e.g. HKT) before working on async, and build on top of that? (of course then you can go even further and ask why there's no I/O monad either) Don't misunderstand me, I …

You can find some discussion on why Rust did not just use monads here . Search in particular for comments by withoutboats and steveklabnik.

Thanks for all the comprehensive replies everyone. Again much more that I could have hoped for. There is a lot there and it will take me some time to get a grip on it all. I'll get back with comments later. I'm not much closer to putting my finger on a monad yet. Rust analyzer was popping up messag…

What is a monad? And who needs Haskell anyway?

TomP July 12, 2020, 12:48pm 7

Thank you, @alice. This explains Haskell's do notation in a way that many of us can grok, and thus serves to unify related concepts in Rust.

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What is a monad? And who needs Haskell anyway?

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