FP didn't invent immutable data, or mathematical functions. It just makes it easier to use them for some domains, while complicating others.
Imperative programs can have isolated, pure subsections of functionality which are based on composition and immutability, without having to deal with the "ideological" strictness of FP.
You're considering only a minute aspect of large systems. Any real banking system has much more than a ledger to deal with. And most of it involves huge amounts of state, which you can't just pile on top of RAM, or waste CPU on. Anything that doesn't serve a real business/user purpose is just waste.
And text editors don't need FP to support undo either. I'm not sure what point are you trying to make.
The most successful editors in the market, supporting all the features you mentioned, do quite fine with imperative, and in fact, I'm not aware of any meaningful editor written in a FL.
> Memory is cheap now
Not really. This comment strikes me as if it comes from someone who never dealt with significant amount of data.
FP can be extremely wasteful; take head-tail lists for example, which are the default container in many FPs. They waste object-container data, pointer data, and scatter the list items, causing cpu cache misses.
Claiming that imperative is only better for low-level is extremely disconnected from reality. Try writing a game with FP, and I assure you no one will care for code "beauty" when FPS sucks.
Sometimes, arguing with FP purists feels like debating socialists.
Also: go ahead and downvote me, as apparently FP zealots can't tolerate questioning their religion.
> Imperative programs can have isolated, pure subsections of functionality which are based on composition and immutability.
And functional programming languages can support imperative programming and mutation, even Haskell. It's a question of what should be the default, which depends on the domain you are working in.
> Any real banking system has much more than a ledger to deal with.
Most banking systems are cobbled together from third-party components and libraries. Low-level languages aren't really needed. Many banks use Python, which is orders of magnitude slower than Haskell.
> This comment strikes me as if it comes from someone who never dealt with significant amount of data.
Actually I have a background in distributed computing, where functional programming abstractions have made processing large amounts of data much easier (MapReduce, Spark).
> FP can be extremely wasteful; take head-tail lists for example, which are the default container in many FPs.
This is a strawman. I can write inefficient code in any language. C++ code can be littered with pointer indirection and memory barriers.
> Sometimes, arguing with FP purists feels like debating socialists.
Imperative programs can have isolated, pure subsections of functionality which are based on composition and immutability, without having to deal with the "ideological" strictness of FP.
You're considering only a minute aspect of large systems. Any real banking system has much more than a ledger to deal with. And most of it involves huge amounts of state, which you can't just pile on top of RAM, or waste CPU on. Anything that doesn't serve a real business/user purpose is just waste.
And text editors don't need FP to support undo either. I'm not sure what point are you trying to make.
The most successful editors in the market, supporting all the features you mentioned, do quite fine with imperative, and in fact, I'm not aware of any meaningful editor written in a FL.
> Memory is cheap now
Not really. This comment strikes me as if it comes from someone who never dealt with significant amount of data.
FP can be extremely wasteful; take head-tail lists for example, which are the default container in many FPs. They waste object-container data, pointer data, and scatter the list items, causing cpu cache misses.
Claiming that imperative is only better for low-level is extremely disconnected from reality. Try writing a game with FP, and I assure you no one will care for code "beauty" when FPS sucks.
Sometimes, arguing with FP purists feels like debating socialists.
Also: go ahead and downvote me, as apparently FP zealots can't tolerate questioning their religion.