Functional programming - Re: NetBSD's i386 support, was Re: [cctalk] Old UNIX Systems

On Fri, Jun 07, 2013 at 09:44:36PM -0700, Guy Sotomayor wrote: There is a certain amount of confusion forming in this thread. It is idiomatic in functional programming to use recursion for things that would normally be done with iteration in imperative languages. This is because "variables" aren't, and you can't assign new values to them. That means no loop counters, for example. So one "cheats" by creating a little helper function into which the value you want to change is passed into it, and which calls itself where necessary. The compiler's optimiser then uses tail-call optimisation to turn it back into a loop again! There are two reasons for the immutability of variables. The first reason is because ivory-tower computer scientists are really crusty old mathematicians at heart and that's what the theory dictates. I think these people should get out more. The second reason is one I am much more interested in. Because variables are immutable, this means data structures can be shared between threads without having to faff around with atomic updates and locking. This takes away some incredibly hard-to-debug problems with synchronisation and data corruption. In real-world code, you need a hybrid approach, which is why I've a certain fondness for Scala which allows me to use functional most of the time, but also drop in imperative code in hot spots that need a bit more performance.