A modern programming language that makes developers happier.

kotlinlang

I’m reading <https://adventures92.medium.com/kotlin-arrow-kt-eval-monad-a-beginners-guide-bff50e49d07c> and I’m struggling to understand what’s the point of `Eval`.
• `Eval.now` - the author says that “This is the equivalent of just calling a function normally in Kotlin.”
• `Eval.later` - how is it different from `lazy` delegated property?
• `Eval.always` - how is it different from just calling a function each time?
I presume that the examples in the article didn’t fully utilize the power of this monad, like chain it in a creative way. Is it the case? If not, I’d be grateful for any explanation on the above :point_up:

<@UR4QK0YG0> :slightly_smiling_face: just noticed you’re here on Slack

<https://github.com/arrow-kt/arrow/pull/2921> :sweat_smile:

ok, that’s a bit of a bummer from the article’s perspective :smile: could you reveal why you decided to remove them?

&gt; I’m struggling to understand what’s the point of `Eval`.
On the JVM we have the issue of stack-safety, and when working over `F`, or wrappers, you cannot use `tailrec`. So we there is a need to resort to special tricks to make wrappers stack-safe.

Originally the point of `Eval` was to create stack-safe implementations of `Traverse`, but we have since then overcome this need and found simpler solutions.

I.e. we can use `tailrec` with `suspend`, and you can use `bind` with `Iterable#map` etc. So the need for `Eval` has kind-of disappeared within the use-case of `wrappers`.
The Kotlin Std has since then also added `DeepRecursiveFunction` which when we originally had `Eval` did not exist.

I guess this article need an update and a bit more explanation. 
Thanks you <@UQX3ZNU12> for picking it out. 

<@UR4QK0YG0> if you want someone to proof read feel free to share it here or in <#C8UK6RTHU|arrow-contributors> :relaxed: There is plenty of people happy to help!

Same goes for other blogs you plan to write :wink:

Thanks <@U0RM4EPC7> thanks a ton for your valuable feedback.