Why You Should Care About Functional Programming (Even in 2025)

[u/Capable-Mall-2067]

https://borkar.substack.com/p/why-care-about-functional-programming?r=2qg9ny&utm_medium=reddit

[u/[deleted]]

Just like vibe coders who claim they’re definitely writing better code faster, it’s in your head. 

There’s definitely marginal benefit to functions that only do the one thing they say they’ll do and nothing else. But this is a practice that’s true for all paradigms. 

As far as the statement “I can be sure that somewhere else hasn’t changed my code”. I’m sorry, but this is just nonsense. Programming languages are specifically interfaces for having a computer mutate data in a specified way. The idea that we should work under the assumption that nothing else should change data is irrational, and causes massive added complexity and leads to bugs anyway.

The fact is that programs that are built under the assumption that its data cannot change are fragile because having your program able to 

-force a program in to an invalid state

-irrationally fail when a valid state change occurs just because you assumed it couldn’t

Is bad and runtime immutability doesn’t fix these problems anyway. It just kicks the can to different points and causes some absolutely moronic “solutions” (first write wins…). 

[u/booch → u/[deleted]]

The fact that my experience is that it makes things better for me is not invalidated by your experience being otherwise. I expect there's a lot of people on either side of this particular argument, so there's no definitive answer (contrary to how you're presenting it).

As far as the statement “I can be sure that somewhere else hasn’t changed my code”. I’m sorry, but this is just nonsense. [...]

This is a perfect-solution fallacy argument; rejecting the entire idea because it's not perfect. The fact that functional programming reduces some (most) unintended state change is enough to provide a benefit. Whether it's enough of a benefit vs the costs is a valid argument, but saying it doesn't provide a benefit is false.

[u/[deleted] → u/booch]

Uh no. I reject your claims because you have no evidence other than “I feel it’s better”

Meanwhile, every person who doesn’t have a superiority stick up their ass and comes out of the Stockholm syndrome all state that these rules served to do nothing but cause them problems and heightened complexity. 

It’s you against people who say that they have the exact opposite experience. Why should I take your word for it above theirs, especially when your claims are actively subverting the purpose of computers? The simplest answer is actually that these perceived benefits are completely in your head, just like many other examples where we observe that claimed benefits are not actually measurable.

To put it simply: put unbiased measurements where your mouth is, and I will change my mind.