closures

Can anybody explain an example in Paul Graham's ANSI Common Lisp page 110? The example try to explain the use &rest and lambda to create functional programming facilities. One of them is a function to compose functional arguments. I cannot find anything explaining how it worked. The code is as follows: (defun compose (&rest fns) (destructuring-bind (fn1 . rest) (reverse fns) #'(lambda (&rest args) (reduce #'(lambda (v f) (funcall f v)) rest :initial-value (apply fn1 args))))) The usage is: (mapcar (compose #'list #'round #'sqrt) '(4 9 16 25)) The output is: ((2) (3) (4) (5)) Line 2 and 6 look

This question already has answers here : What does (function($) {})(jQuery); mean? (6 answers) Possible Duplicate: What does (function($) {})(jQuery); mean? I've seen a lot of jQuery code with the following sort of syntax, but I don't really understand what it means. It shows up in this answer and this answer on a question about code organization. Both talk about namespacing, so I'm guessing that's what it accomplishes. var foo = (function () { var someVar; function someFunc() { return true; } })(); Is this for namespacing, and how does it work? Sometimes there is a name (the namespace?) in

I was just wondering if it was possible to pass a function to a button action (which is usually a selector). For example, normally I'd say: UIBarButtonItem(title: "Press", style: .Done, target: self, action: "functionToCall") func functionToCall() { // Do something } But I was wondering if it's possible to do something like: UIBarButtonItem(title: "Press", style: .Done, target: self, action: { // Do Something }) Reason I want to do this is because my function is super simple and it seems like it would be neater and more Swift-like what with the emphasis they are placing on closures. Here's an

WordPress hooks can be used in two ways: using callback function name and appropriate function add_action( 'action_name', 'callback_function_name' ); function callback_function_name() { // do something } using anonymous function (closure) add_action( 'action_name', function() { // do something } ); Is there any difference for WordPress what way to use? What is prefered way and why? TeeDeJee The disadvantage of the anonymous function is that you're not able to remove the action with remove_action . Important: To remove a hook, the $function_to_remove and $priority arguments must match when the