Recursion

joshighanshyam · #1 (**permalink**) 12-02-2008

I want to halt a tail recursive function after certain validation. I want to come out of entire recursion without unwinding phase. How can i achieve that . The coding is done in C language.

vino · #2 (**permalink**) 12-02-2008

Quote:

Originally Posted by joshighanshyam

I want to halt a tail recursive function after certain validation. I want to come out of entire recursion without unwinding phase. How can i achieve that . The coding is done in C language.

Is there any reason you are not taking the iterative approach ?

otheus · #3 (**permalink**) 12-02-2008

You've been around long enough not to post homework questions, so I'll answer: use setjmp() and longjmp(). Basically, the first call saves the current stack configuration (stack pointer, parent caller address, etc). The second call restores that stack configuration. So you might have some code like this:

Code:

#include <setjmp.h>
int found = 0;
jmp_buf origin; 
main() {
  setjmp(&origin);
  if (found == 0) 
     recursive_call();
}

recursive_call() {

   /* HERE: set found to 1 at some point */
   /* then... */
   if (found == 0) 
      recursive_call();
   else 
      longjmp( &origin );
}

esther.david6 · #4 (**permalink**) 12-03-2008

A procedure that is applied once, and then applied to the result of that application, and so on. A recursive definition defines the result of some operation for 0, and then the result for any number n + 1 in terms of the result for n; thus the operation becomes defined for all numbers (the notion may be extended to describe the same process on any well-ordered set).

otheus · #5 (**permalink**) 12-03-2008

Esther/Daid, I don't think the user wants to know WHAT a recursive procedure is. He wants to know how to exit the procedure while skipping all the returns and function clean-up.

joshighanshyam · #6 (**permalink**) 12-03-2008

Thanks you all for your valuable Feedbacks

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