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Messages - Zabolekar

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#1
newLISP in the real world / Re: (define ...) inside a default value
July 26, 2014, 10:54:04 AM
Thanks.
#2
newLISP in the real world / Re: (define ...) inside a default value
July 25, 2014, 07:03:19 AM
Thanks for the answer! So the old function definition is collected right after we redefine the function? That makes sense for me. Then, as far as I understand, modifying the function without actually redefining it should be safe (is it?):


Code Select
(define (f a (b (setf (nth 1 f) "D"))) a)
(println (f "A" 1) (f "B") (f "C"))

It  prints ADD, as expected.



Is there a way to self-modify a function so that the changes only take place after the function returns?
#3
newLISP in the real world / (define ...) inside a default value
July 24, 2014, 09:31:45 PM
I have no reason to use something like that in real code, so this is just pure curiosity. Nevertheless, I would like to understand why this piece of code does what it does.



In newLisp, the following code


Code Select
(define (f a (b (define (f a) "D"))) a)
(println (f "A" 1) (f "B") (f "C"))

will print AnilD. I don't quite understand where nil comes from. I would expect either ABD or, less intuitive but still understandable, ABC. It gets even more confusing. When I do


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(define (f a (b (define (f a) "D"))) (println "") a)
(f "A")

the interpreter tells me:


Code Select
--- cannot execute: restart shell ---

And, indeed, in this case I have to restart the shell to make it work again.



In Common Lisp, Clojure and Ruby the following pieces of code seem to be equivalent:


Code Select
(defun f (a &optional (b (defun f (a) "D"))) a)
(format t "~a~a~a" (f "A" 1) (f "B") (f "C"))

Code Select
(defn f ([a] (defn f [a] "D") a) ([a b] a))
(println (str (f "A" 1) (f "B") (f "C")))

Code Select
def f(a, b = def f(a); "D"; end); a; end
p f("A", 1) + f("B") + f("C")

All of them print ABD.
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