this post was submitted on 10 Sep 2023
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If you use JavaScript, you've probably seen a monad, since Promise is a monad. Unit is
Promise.resolve()
, bind isPromise.then()
. As required,Promise.resolve(x).then(y) === y(x)
(unit forms a left identity of bind),y.then(Promise.resolve) === y
(unit forms a right identity of bind), andx.then(y.then(z)) === x.then(y).then(z)
(bind is essentially associative).You even have the equivalent of Haskell's fancy do-notation (a form of syntactic sugar to save writing unit and bind all over the place) in the form of async/await. It's just not generalized the way it is in Haskell.