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Here's the link where he discusses functional programming style: https://web.archive.org/web/20170116040923/http://gamasutra.com/view/news/169296/Indepth_Funct

Here's the link where he discusses functional programming style: https://web.archive.org/web/20170116040923/http://gamasutra.com/view/news/169296/Indepth_Functional_programming_in_C.php https://web.archive.org/web/20170116040923/http://gamasutra.... He does not say that that his email is completely outdated - he just says that calling pure functions is exempt from the inlining rule. He's not off writing pure FP now. His approach is still deeply pragmatic. In the link above he discusses degrees of function purity. "Pure FP" has a whole different connotation - where whole programs are written in that constrained style.

ninetyninenine 2y ago
He literally said he’s bullish on pure fp. Which means he is off writing pure fp. His own article about it never explicitly or implicitly implies a “pragmatic approach”. I never said he said his email was completely outdated. He for sure implies it’s outdated and updates us on his views of inlining which I also mentioned.
- coob 2y ago
  > I never said he said his email was completely outdated. From your prior message: > Carmack called his email completely outdated
  - ninetyninenine 2y ago
    Ok my bad but I did mention what he’s doing with inlining. So I contradicted myself in the original message which you didn’t identify. He still does inlining.
    - deleted 2y ago
      [deleted]
solomonb 2y ago
The original article literally starts with this: > In the years since I wrote this, I have gotten much more bullish about pure functional programming, even in C/C++ where reasonable: (link) > >The real enemy addressed by inlining is unexpected dependency and mutation of state, which functional programming solves more directly and completely. However, if you are going to make a lot of state changes, having them all happen inline does have advantages; you should be made constantly aware of the full horror of what you are doing. He explicitly says that functional programming solves the same issue as inlining but more directly and completely.
- cellularmitosis 2y ago
  Maybe this is just a subtle semantic thing, but what I took from this is that he is factoring out pure functions where ever possible, within a procedural context. In my mind, that’s not the same thing as “functional programming”.
pragma_x 2y ago
Thank you for this. I appreciate that this (classic) article lays bare the essence of FP without the usual pomp and "use Lisp/Scheme/Haskell already" rhetoric. My takeaway is that FP is mostly about using functions w/o side effects (pure), which can be achieved in any programming language provided you're diligent about it.
- zelphirkalt 2y ago
  This is a bit naive though. It depends on what you want to do and whether the language you are using offers the required primitives and other things like persistent functional data structures. Without those, you will find yourself hard-pressed to make FP happen. It is of course usually possible with most languages (except those where primitives are already mutating and therefore infectiously prevent you from writing pure functions), but it might not be idiomatic at all, or might not be feasible to roll all things your own, to replace any mutating basics. For example imagine having to copy a data structure all over the place again and again, because its methods are mutating its internal state. That would be inefficient, much more inefficient than a well written corresponding functional data structure, and it would be ugly code. Are you going to write that extra data structure, when your task is actually something else? Some management breathing down your neck, asking when something will be done? Or not so well versed coworkers complaining about you adding a lot of code that might need to be maintained by them, while they don't understand FP? Do you even have the knowledge to implement that data structure in the first place, or will you need to study a couple of papers and carefully translate their code, if any, i to your language and then verify expected performance in meaningful benchmarks? Lots of problems can arise there in practice.
- ninetyninenine 2y ago
  No functional programming is about programming as if your code is a math equation. In math people never use procedures. They write definitions in math in terms of formulas and expressions. If you can get everything to fit on one line in your programming. Then you are doing functional programming. The lack of side effects, lack of mutation and high modularity are the beneficial outcome of fp, it is not the core of what you're doing. The core of what you're doing is your defining your program as a formula/equation/expression rather then a list of procedures or steps. Of course, why you would write your program this way is because of the beneficial outcomes. By coincidence if you write your code in a way where you just account for the side effects like deliberately avoiding mutation, IO and side effects... then your program will become isomorphic to a mathematical function. So it goes both ways. Another thing you will note and most people don't get this is that for loops don't exist in FP. The fundamental unit of "looping" in fp is always done with recursion, just like how they would do it in mathematical expressions.

ninetyninenine 2y ago

He literally said he’s bullish on pure fp. Which means he is off writing pure fp. His own article about it never explicitly or implicitly implies a “pragmatic approach”. I never said he said his email was completely outdated. He for sure implies it’s outdated and updates us on his views of inlining which I also mentioned.

coob 2y ago
> I never said he said his email was completely outdated. From your prior message: > Carmack called his email completely outdated
- ninetyninenine 2y ago
  Ok my bad but I did mention what he’s doing with inlining. So I contradicted myself in the original message which you didn’t identify. He still does inlining.
  - deleted 2y ago
    [deleted]

solomonb 2y ago

The original article literally starts with this: > In the years since I wrote this, I have gotten much more bullish about pure functional programming, even in C/C++ where reasonable: (link) > >The real enemy addressed by inlining is unexpected dependency and mutation of state, which functional programming solves more directly and completely. However, if you are going to make a lot of state changes, having them all happen inline does have advantages; you should be made constantly aware of the full horror of what you are doing. He explicitly says that functional programming solves the same issue as inlining but more directly and completely.

cellularmitosis 2y ago
Maybe this is just a subtle semantic thing, but what I took from this is that he is factoring out pure functions where ever possible, within a procedural context. In my mind, that’s not the same thing as “functional programming”.

pragma_x 2y ago

Thank you for this. I appreciate that this (classic) article lays bare the essence of FP without the usual pomp and "use Lisp/Scheme/Haskell already" rhetoric. My takeaway is that FP is mostly about using functions w/o side effects (pure), which can be achieved in any programming language provided you're diligent about it.

zelphirkalt 2y ago
This is a bit naive though. It depends on what you want to do and whether the language you are using offers the required primitives and other things like persistent functional data structures. Without those, you will find yourself hard-pressed to make FP happen. It is of course usually possible with most languages (except those where primitives are already mutating and therefore infectiously prevent you from writing pure functions), but it might not be idiomatic at all, or might not be feasible to roll all things your own, to replace any mutating basics. For example imagine having to copy a data structure all over the place again and again, because its methods are mutating its internal state. That would be inefficient, much more inefficient than a well written corresponding functional data structure, and it would be ugly code. Are you going to write that extra data structure, when your task is actually something else? Some management breathing down your neck, asking when something will be done? Or not so well versed coworkers complaining about you adding a lot of code that might need to be maintained by them, while they don't understand FP? Do you even have the knowledge to implement that data structure in the first place, or will you need to study a couple of papers and carefully translate their code, if any, i to your language and then verify expected performance in meaningful benchmarks? Lots of problems can arise there in practice.
ninetyninenine 2y ago
No functional programming is about programming as if your code is a math equation. In math people never use procedures. They write definitions in math in terms of formulas and expressions. If you can get everything to fit on one line in your programming. Then you are doing functional programming. The lack of side effects, lack of mutation and high modularity are the beneficial outcome of fp, it is not the core of what you're doing. The core of what you're doing is your defining your program as a formula/equation/expression rather then a list of procedures or steps. Of course, why you would write your program this way is because of the beneficial outcomes. By coincidence if you write your code in a way where you just account for the side effects like deliberately avoiding mutation, IO and side effects... then your program will become isomorphic to a mathematical function. So it goes both ways. Another thing you will note and most people don't get this is that for loops don't exist in FP. The fundamental unit of "looping" in fp is always done with recursion, just like how they would do it in mathematical expressions.