> Coming from a C++ background I'm not that familiar with functions as > first class values. We sort of do have them in C++ - as functors - ie > a class that has the function invocation operator defined. This class > can have storage as well, which means you can have a functor object > type which then can have particular instances instantiated with > different particular parameters stored with the object instance. > > I'm wondering whether this is effectively what Clojure does > under-the-hood, or whether it does something different / more > sophisticated.
Okay. Functions as values. Go look at the IFn interface, https://github.com/clojure/clojure/blob/master/src/jvm/clojure/lang/IFn.java. In C or C++ you can take a raw machine pointer to a function. The JVM does not allow for this behavior the result of which is that whenever you have a "function" really what you have is a function-like object with the standard application/invocation member methods. Nothing really sophisticated here, a single class is naively generated for each fn in your program and a fn that returns a fn simply creates a new instance of that fn and returns it since there's no other way that we can take a function "as a value" prior to JVM 1.8 which has bytecode lambdas and which the reference Clojure implementation doesn't leverage yet if ever. The "standard" Clojure compiler is pretty braindead when it comes to the emitted bytecode, but this is due to the philosophy (backed up by experience) that the JIT is typically good enough. You could generate better code, and my GSoC project is research into doing so but the reality of Clojure programs is that function calls even with Var indirection are free in comparison to the performance hits we take due to using immutable datastructures and eschewing in place updates. Reid -- 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 --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
