I'm currently reading the article about STM here: http://java.ociweb.com/mark/stm/article.html

From the article, it seems that Promises are a mechanism that performs serial execution of asynchronous tasks, by having them performed serially. In comparison, Atoms are a mechanism to share state between asynchronous tasks, without having them run serially, to potentially reduce the overall time. From the article: > There are two general categories of multithreaded software. In one category the goal is to divide the work involved in processing a single "job" into pieces and run the pieces concurrently in order to complete the job sooner. In the other category the goal is to coordinate the execution of multiple "jobs", allowing them to execute concurrently so that as a group they complete sooner than if they were run serially. In both cases there can be contention over the data being accessed. However, the issue is perhaps more common and harder to avoid in the second category.

So Promises are of the first kind, and Atoms are of the second kind of concurrent mechanisms described

Atoms are totally disticnt from STM. the reference type that participates in STM is ref, and the update fns alter, commute

you can have any amount of promises you want using the same atom, so that would be a way in which they are different.

when a promise is resolved it can't change it's value, atoms can change their value at every deference

for these i fork the repo, add a deps.edn, and typically things work. make sure you transfer the project.clj deps over accurately.

also, i'm not sure having a :tag, and :sha makes sense, i thought a tag referred to a sha

you can use this as a maven-style dependency to fetch from clojars rather than git... I think deps can only use deps and poms as manifest types

specifying a tag also requires at least a short SHA to ensure that the tag hasn't moved: <https://clojure.org/reference/deps_and_cli#_coord_attributes>

what Bob said is how it was explained to me

re: maven-style deps How can I do that, is there an example?

on that library's GH page, at the top of the readme, there's a clojars badge (gray and orange) - following that link provides coordinates in several styles, including a Clojure CLI/deps.edn format

I include this longish explanation because that clojars badge is fairly common, and I think it's a decent trick to know

oh thanks for pointing that out. I'll be sure to check that next time

thanks for your help, was able to build correctly

oh, i thought this question was about using git, didn't think the dep was on maven.

A monadic way was popularized https://fsharpforfunandprofit.com/rop/ as "railway oriented programming" and works fine in Clojure. Another instance is Zach Tellman's "Manifold" library for Clojure, wherein the centerpiece, the "Deferred" thing, resolves to either a successful value or an error. Manifold thereby overcomes a weakness of host Exceptions, which is their rocky path to the interested client, which might be on another thread.

Exceptions are fine, if you throw ex-info you can put any key you want in it then write a multi method to dispatch on it. Another option is using cognitect/anomalies, a good example of which can be found in the aws client lib

Okay. Thank you for answers!