Re: How does this code works.

[Zach Allaun]

I'm new to clojure as well, so someone please correct me if the following 
explanation is wrong, but I'll give it a shot :).

The JVM does not natively support TCO; clojure uses the recur form to 
accomplish what is effectively the same thing despite that shortcoming of 
its host. The recur form works by jumping back to either the loop (or, if 
there is no loop form, the defn/fn), and rebinding those scoped variables 
to the value of the recur's arguments.

In your example:

(loop [n number factorial 1];; This will be the "target" of the 
recur
   (if (zero? n)   ;; If n is zero,
 factorial  ;; return the value of 
factorial
 (recur (dec n) (* factorial n;; otherwise, jump to the loop, 
rebinding n to (dec n) and factorial to (* factorial n)

I hope that this made sense :).

On Sunday, April 15, 2012 11:37:35 AM UTC-4, Anto wrote:
>
> I'm very new to Clojure. And I was pretty much interested to learn 
> about vectors, list . maps in clojure. 
>
> I have a code like this : 
>
> (defn factorial-1 [number] 
>   "computes the factorial of a positive integer 
>in a way that doesn't consume stack space" 
>   (loop [n number factorial 1] 
> (if (zero? n) 
>   factorial (recur (dec n) (* factorial n) 
>
> (println (time (factorial-1 5))) 
>
>
> which argues that it does tail recursion optimization. I found this 
> code on net. Can anyone explain me what does the last three lines 
> does: 
>
>  (loop [n number factorial 1] 
> (if (zero? n) 
>   factorial (recur (dec n) (* factorial n 
>
> Thanks in advance.

-- 
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

Re: How does this code works.

[Roberto Mannai]

if (n == 0) return the "factorial", else go to the "loop label" and recur
with the two parameters (n--)  and (factorial * n). Go on until n-- reaches
0.

In a Java-like translation we could have:

int n = number;
factorial = 1;

while(n > 0){
   factorial *= n--;
}
return factorial;



On Sun, Apr 15, 2012 at 5:37 PM, Anto  wrote:

> Can anyone explain me what does the last three lines
> does:
>
>  (loop [n number factorial 1]
>(if (zero? n)
>  factorial (recur (dec n) (* factorial n
>
> Thanks in advance.
>
> --
> 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 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

How does this code works.

[Anto]

I'm very new to Clojure. And I was pretty much interested to learn
about vectors, list . maps in clojure.

I have a code like this :

(defn factorial-1 [number]
  "computes the factorial of a positive integer
   in a way that doesn't consume stack space"
  (loop [n number factorial 1]
(if (zero? n)
  factorial (recur (dec n) (* factorial n)

(println (time (factorial-1 5)))


which argues that it does tail recursion optimization. I found this
code on net. Can anyone explain me what does the last three lines
does:

 (loop [n number factorial 1]
(if (zero? n)
  factorial (recur (dec n) (* factorial n

Thanks in advance.

-- 
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