The answer would be a mix of A and B, mostly because there seems to be an assumption that you have to consider concurrency everywhere in order to be able to have it at some point later. This is not the case.
You do tend to be very explicit about concurrency and only use the concurrency primitives (refs, atoms, agents and vars) at a few selected spots, but most of the time you don't have to think about concurrency at all, since even the smallest parts of the system is written in a way that allows for concurrency (by using pure functions and not using the concurrency primitives). Clojure is a functional programming language, which among other things means that computation is in general carried out using referentially transparent (pure) functions. A pure function always return the same value for the same input and is free from side-effects. Pure functions are always thread safe and will never be any problem to concurrency. In a language like Java, mutation of variables and objects is very often used for performing computations. But this intervenes calculations that has nothing to do with each other, since a mutating step in computation A can affect computation B if they operate on the same objects. The result is that in Java, you have to think about concurrency when you perform computations, unlike in Clojure. (Here, I use the word "compute" to mean something like "produce new data of interest".) You tend to write the largest part of a Clojure application as compositions of pure functions. You only have to introduce reference primitives when you have a long-running process whose state changes and evolves over time (for instance a game or a server, or anything that communicates with the outside world and changes thereafter). Clojure acknowledges the need for things to be able to change, but keeps that separate from computation. Most library code I have written hasn't used the concurrency primitives at all. The state changing part of an application often resides at a higher level. // raek -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
