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Except this “simple” metaphor isn’t too useful. For monads like IO and State, “monad as a container” is a stretch. And some don’t fit at all — the list monad of
by tylerhou 7y ago
Except this “simple” metaphor isn’t too useful. For monads like IO and State, “monad as a container” is a stretch. And some don’t fit at all — the list monad often is imagined as a computational context with nondeterminism, not simply a container.
https://byorgey.wordpress.com/2009/01/12/abstraction-intuition-and-the-monad-tutorial-fallacy/ https://byorgey.wordpress.com/2009/01/12/abstraction-intuiti...
- mikekchar 7y agoI don't really understand your point of view. Especially the list monad is literally a list. The shape of bind for the list monad is [a] -> (a -> [b]) -> [b]. If that's not a container, I don't know what is. The fact that it can be used to solve problems where the list represents a non-deterministic result is really secondary. I mean, I suppose you can think of it as being different, but it seems a lot more complicated in my mind. I think some "containers" a definitely hard to envision. A partially applied function is also a monad (i.e. it's trivial to write a meaningful bind for it). It may be hard to think of a partially applied function as "containing" the applied parameters, but I still think that's easier than any other way of envisioning it. But maybe it's a matter of horses for courses.
- pjc50 7y agoFor IO, the monad is a "box" you put the entire mutable universe in so you can pretend the rest of your program is stateless.