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Functional programming and reliability: ADTs, safety, critical infrastructure

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Re: Functional programming and reliability: ADTs, safety, critical infrastructure

#11

Post by saghm »

mlavrent wrote: post #2

This article seems to conflate strong type systems with functional programming, except in point 8. It makes sense why- OCaml and Haskell are functional and were early proponents of these type systems. But, languages like Racket don’t have these type systems and the article doesn’t do anything to explain why they are _also_ better for reliability.

I've seen it pointed out that the main point of functional programming is immutability, and that the benefits mostly flow from that. I haven't really learned much of any lisp dialect, but my (admittedly fuzzy) general perception is that this is also the preferred way to work in them, so my guess is that's where the benefit in reliability might come from.

Re: Functional programming and reliability: ADTs, safety, critical infrastructure

#12

Post by d--b »

Strong types: yes, it’s definitely better

Functional programming: no, functional programming as in: the final program consists in piping functions together and calling the pipe. In my opinion, that tends to get in the way of complex error handling.

The problem being that raising Exceptions at a deep level and catching them at some higher level is not pure functional programming. So your code has to deal with all the cases. It is more reliable if you can do it, but large systems have way too many failure points to be able to handle them all in a way that is practical.

Re: Functional programming and reliability: ADTs, safety, critical infrastructure

#13

Post by saghm »

henning wrote: post #7

I like good type systems, too, but they won't save you from bugs that are better addressed by fuzz testing, fault injection testing and adversarial mindset shifts.

Luckily these aren't exclusive! You can do all of those things with a strong type system as well, and get the benefits of all of them.

Re: Functional programming and reliability: ADTs, safety, critical infrastructure

#14

Post by zelphirkalt »

saghm wrote: post #11
mlavrent wrote: post #2

This article seems to conflate strong type systems with functional programming, except in point 8. It makes sense why- OCaml and Haskell are functional and were early proponents of these type systems. But, languages like Racket don’t have these type systems and the article doesn’t do anything to explain why they are _also_ better for reliability.

I've seen it pointed out that the main point of functional programming is immutability, and that the benefits mostly flow from that. I haven't really learned much of any lisp dialect, but my (admittedly fuzzy) general perception is that this is also the preferred way to work in them, so my guess is that's where the benefit in reliability might come from.

Correct. If things are mutable, then in most languages, there can be spooky action at a distance, that mutates some field of some other object or does so indirectly via some calls. This then can change how the thing behaves in other circumstances. This style of programming quickly becomes hard to fully grasp and leads to humans making many mistakes. Avoiding mutation therefore avoids these kinds of faults and mistakes.

Re: Functional programming and reliability: ADTs, safety, critical infrastructure

#15

Post by bdangubic »

conartist6 wrote: post #4
mlavrent wrote: post #2

This article seems to conflate strong type systems with functional programming, except in point 8. It makes sense why- OCaml and Haskell are functional and were early proponents of these type systems. But, languages like Racket don’t have these type systems and the article doesn’t do anything to explain why they are _also_ better for reliability.

You don't need a strong type system or even really ANY compile-time type system for this strategy to work! I use all these techniques in plain JS and I can still get the benefits of correct-by-construction code style just by freezing objects and failing fast.

godspeed with that :)

Re: Functional programming and reliability: ADTs, safety, critical infrastructure

#16

Post by cubefox »

I think there is a strong case that ADTs (algebraic data types) aren't so great after all. Specifically, the "tagged" unions of ADT languages like Haskell are arguably pretty clearly inferior to the "untagged" unions of TypeScript or Scala 3. Because the latter actually behave like a logical "or" rather than an artificial construct that needs to be wrapped and unwrapped.

Re: Functional programming and reliability: ADTs, safety, critical infrastructure

#17

Post by agumonkey »

conartist6 wrote: post #4
mlavrent wrote: post #2

This article seems to conflate strong type systems with functional programming, except in point 8. It makes sense why- OCaml and Haskell are functional and were early proponents of these type systems. But, languages like Racket don’t have these type systems and the article doesn’t do anything to explain why they are _also_ better for reliability.

You don't need a strong type system or even really ANY compile-time type system for this strategy to work! I use all these techniques in plain JS and I can still get the benefits of correct-by-construction code style just by freezing objects and failing fast.

Is this a methodology you use at work or only for personal projects ? I'm curious how common this culture is among companies/teams.

Re: Functional programming and reliability: ADTs, safety, critical infrastructure

#18

Post by zelphirkalt »

d--b wrote: post #12

Strong types: yes, it’s definitely better Functional programming: no, functional programming as in: the final program consists in piping functions together and calling the pipe. In my opinion, that tends to get in the way of complex error handling. The problem being that raising Exceptions at a deep level and catching them at some higher level is not pure functional programming. So your code has to deal with all the…

If you have strong types, it is still possible to make a mutable thing, that will be mutated from the other end of the program and that will introduce bugs, that can be hard to find. If you are doing FP on the other hand, at least change always results in new objects, with structural sharing at most. This excludes a whole category of bugs.

Re: Functional programming and reliability: ADTs, safety, critical infrastructure

#19

Post by whateveracct »

> In banking, telecom, and payments, reliability is not a nice to have. It is table stakes.

Haha as someone who has worked in one of these domains using FP even - I wish the people in charge agreed with you!

Reliability is a cost center and Product-oriented Builders treat it as such.

Re: Functional programming and reliability: ADTs, safety, critical infrastructure

#20

Post by jesse__ »

cubefox wrote: post #16

I think there is a strong case that ADTs (algebraic data types) aren't so great after all. Specifically, the "tagged" unions of ADT languages like Haskell are arguably pretty clearly inferior to the "untagged" unions of TypeScript or Scala 3. Because the latter actually behave like a logical "or" rather than an artificial construct that needs to be wrapped and unwrapped.

> "tagged" unions of ADT languages like Haskell are arguably pretty clearly inferior to the "untagged" unions of TypeScript

dude .. wut?? Explain to me exactly how this is true, with a real world example.

From where I stand, untagged unions are useful in an extremely narrow set of circumstances. Tagged unions, on the other hand, are incredibly useful in a wide variety of applications.

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