lisp

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

Now this works just fine: (setq al '((a . "1") (b . "2"))) (assq-delete-all 'a al) But I'm using strings as keys in my app: (setq al '(("a" . "foo") ("b" . "bar"))) And this fails to do anything: (assq-delete-all "a" al) I think that's because the string object instance is different (?) So how should I delete an element with a string key from an association list? Or should I give up and use symbols as keys instead, and convert them to strings when needed? If you know there can only be a single matching entry in your list, you can also use the following form: (setq al (delq (assoc <string> al)

I realize that the first rule of Macro Club is Don't Use Macros, so the following question is intended more as an exercise in learning Clojure than anything else (I realize this isn't necessarily the best use of macros). I want to write a simple macro which acts as a wrapper around a regular (defn) macro and winds up adding some metadata to the defined function. So I'd like to have something like this: (defn-plus f [x] (inc x)) ...expand out to something like this: (defn #^{:special-metadata :fixed-value} f [x] (inc x)) In principle this doesn't seem that hard to me, but I'm having trouble

According to SICP section 1.2.6 , exercise 1.22: Most Lisp implementations include a primitive called runtime that returns an integer that specifies the amount of time the system has been running (measured, for example, in microseconds). I'm using DrScheme , where runtime doesn't seem to be available, so I'm looking for a good substitute. I found in the PLT-Scheme Reference that there is a current-milliseconds primitive. Does anyone know if there's a timer in Scheme with better resolution? current-milliseconds is a function that returns the current millisecond count from the system, but it