Practical introduction to algebraic datatypes (ADTs) in TypeScript • Hacker News Board

Re: Practical introduction to algebraic datatypes (ADTs) in TypeScript

#21

Post by jhanschoo » Thu, Aug 12, 2021, 5:07 AM UTC

jimsimmons wrote: post #20

lalaithion wrote: post #3

I think this article makes the "sum" and "product" terms out to be very complicated, when in fact it's quite simple. If we have two enums enum Bool { True, False } enum Status { Waiting, Successful, Failed } We can combine them into a product type, like a tuple, or a sum type, like a union. type Product = (Bool, Status) type Sum = Bool | Status Now, we ask ourselves, what are the valid values of type Product? (True,…

This helps handle IO in pure functional languages because? Is it because functions can have more than 1 type?

Can you elaborate what you mean by that? Support of sum and product types are used everywhere in typed functional languages and I don't know of any way they are exploited specifically in IO in a way that does not generalize to other domains.

Re: Practical introduction to algebraic datatypes (ADTs) in TypeScript

#22

Post by jimsimmons » Thu, Aug 12, 2021, 6:37 AM UTC

jhanschoo wrote: post #21

jimsimmons wrote: post #20

Earlier quoted context omitted.

This helps handle IO in pure functional languages because? Is it because functions can have more than 1 type?

Can you elaborate what you mean by that? Support of sum and product types are used everywhere in typed functional languages and I don't know of any way they are exploited specifically in IO in a way that does not generalize to other domains.

Whoops looks like I confused algebraic datatypes and algebraic effects. Actually this confusion / realization because of your comment just clicked something for me, so thanks!!

Re: Practical introduction to algebraic datatypes (ADTs) in TypeScript

#23

Post by rualca » Fri, Aug 13, 2021, 5:12 PM UTC

lalaithion wrote: post #3

I think this article makes the "sum" and "product" terms out to be very complicated, when in fact it's quite simple. If we have two enums enum Bool { True, False } enum Status { Waiting, Successful, Failed } We can combine them into a product type, like a tuple, or a sum type, like a union. type Product = (Bool, Status) type Sum = Bool | Status Now, we ask ourselves, what are the valid values of type Product? (True,…

> I think this article makes the "sum" and "product" terms out to be very complicated, (...)

Indeed it would drive the point home if instead of simply mentioning product they referred to Cartesian product.

I guess sum types imply adding together two domain, but unless there's a subtlety then union would be clearer as well.