> My pragmatic summary: A large fraction of the flaws in software development are due to programmers not fully understanding all the possible states their code may execute in. In a multithreaded environment, the lack of understanding and the resulting problems are greatly amplified, almost to the point of panic if you are paying attention. Programming in a functional style makes the state presented to your code explicit, which makes it much easier to reason about, and, in a completely pure system, makes thread race conditions impossible.
> I do believe that there is real value in pursuing functional programming, but it would be irresponsible to exhort everyone to abandon their C++ compilers and start coding in Lisp, Haskell, or, to be blunt, any other fringe language. To the eternal chagrin of language designers, there are plenty of externalities that can overwhelm the benefits of a language, and game development has more than most fields. We have cross platform issues, proprietary tool chains, certification gates, licensed technologies, and stringent performance requirements on top of the issues with legacy codebases and workforce availability that everyone faces.
> If you are in circumstances where you can undertake significant development work in a non-mainstream language, I’ll cheer you on, but be prepared to take some hits in the name of progress. For everyone else: No matter what language you work in, programming in a functional style provides benefits. You should do it whenever it is convenient, and you should think hard about the decision when it isn’t convenient.
> My pragmatic summary: A large fraction of the flaws in software development are due to programmers not fully understanding all the possible states their code may execute in. In a multithreaded environment, the lack of understanding and the resulting problems are greatly amplified, almost to the point of panic if you are paying attention. Programming in a functional style makes the state presented to your code explicit, which makes it much easier to reason about, and, in a completely pure system, makes thread race conditions impossible.
> I do believe that there is real value in pursuing functional programming, but it would be irresponsible to exhort everyone to abandon their C++ compilers and start coding in Lisp, Haskell, or, to be blunt, any other fringe language. To the eternal chagrin of language designers, there are plenty of externalities that can overwhelm the benefits of a language, and game development has more than most fields. We have cross platform issues, proprietary tool chains, certification gates, licensed technologies, and stringent performance requirements on top of the issues with legacy codebases and workforce availability that everyone faces.
> If you are in circumstances where you can undertake significant development work in a non-mainstream language, I’ll cheer you on, but be prepared to take some hits in the name of progress. For everyone else: No matter what language you work in, programming in a functional style provides benefits. You should do it whenever it is convenient, and you should think hard about the decision when it isn’t convenient.
-- John Carmack (http://www.altdevblogaday.com/2012/04/26/functional-programm...)