what is recursion in c++.

[athar.mirchi]

..plz define it.

[Pete Becker]

On 2008-01-05 15:19:08 -0500, Salt_Peter <pj*****@yahoo. comsaid:

On Jan 5, 2:17 pm, "athar.mir...@g mail.com" <athar.mir...@g mail.com>
wrote:

>.plz define it.

As the English word suggests: a recursion is simply a function that
calls itself.
Which is neither efficient nor beneficial.

Bummer. We'll have to stop using quicksort.

--
Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
(www.petebecker.com/tr1book)

[red floyd]

at**********@gm ail.com wrote:

.plz define it.

RECURSION: see RECURSION.

[red floyd]

Jim Langston wrote:

recursion [ri-kur'zhen] - (n) see recursion

Damn. I posted the exact same definition before I saw your post. GMTA.

[Jerry Coffin]

In article <m3************ *****@newssvr21 .news.prodigy.n et>,
no*****@here.du de says...

at**********@gm ail.com wrote:

.plz define it.

RECURSION: see RECURSION.

Error stack overflow at 1.

Recursion: if (understood) return; else see Recursion.

--
Later,
Jerry.

The universe is a figment of its own imagination.

[Kira Yamato]

On 2008-01-05 21:30:42 -0500, red floyd <no*****@here.d udesaid:

at**********@gm ail.com wrote:

>.plz define it.

RECURSION: see RECURSION.

That's not recursion. That's just circular reasoning.

The difference is that circular reasoning is not logically sound, but
recursion is. More specifically, a definition using recursion admits
existence and uniqueness of an object under that definition, while
circular reasoning is ambiguous.

For example, the recursion
f(n+1) = f(n) + 1
f(0) = 0
admits the actual function
f(n) = n.

On the other hand, the circular-reasoning "definition "
g(n) = g(n)
admits any function since that definition is vacuously true for any function.

--

-kira

[Daniel T.]

"at**********@g mail.com" <at**********@g mail.comwrote:

.plz define it.

Here is an example of recursion that people don't often think of as
such...

class Foo {
public:
list< Foo* foos;
void bar() {
for_each( foos.begin(), foos.end(), mem_fun( &Foo::bar ) );
}
};

int main() {
Foo f[10];
f[0].foos.push_back ( &f[1] );
f[0].foos.push_back ( &f[2] );
f[0].foos.push_back ( &f[3] );
f[2].foos.push_back ( &f[4] );
f[2].foos.push_back ( &f[5] );
f[2].foos.push_back ( &f[6] );
f[3].foos.push_back ( &f[7] );
f[7].foos.push_back ( &f[8] );
f[8].foos.push_back ( &f[9] );

f[0].bar();
}

[Lionel B]

On Sat, 05 Jan 2008 20:26:10 -0700, Jerry Coffin wrote:

In article <m3************ *****@newssvr21 .news.prodigy.n et>,
no*****@here.du de says...

>at**********@gm ail.com wrote:

.plz define it.

RECURSION: see RECURSION.

Error stack overflow at 1.

Recursion: if (understood) return; else see Recursion.

Warning: condition always evaluates to false

--
Lionel B

[James Kanze]

On Jan 5, 9:19 pm, Salt_Peter <pj_h...@yahoo. comwrote:

On Jan 5, 2:17 pm, "athar.mir...@g mail.com"
<athar.mir...@g mail.comwrote:

.plz define it.

As the English word suggests: a recursion is simply a function
that calls itself. Which is neither efficient nor beneficial.

It's beneficial when its beneficial. On most modern
architectures, it's often as efficient as the alternatives. (I
once benchmarked a recursive version of quick sort, and one
which avoided recursion. the recursive version was faster.)

Each call generates a new local stack which eventually all
need to be unwound. So in C++, its usually replaced with
better alternatives. An example of a preferred alternative
would then be a function object (functor).

How is that relevant to recursion. A functional object is still
a function, and can still be recursive or not, according to how
you write it.

Recursive functions have no state (what does that mean?).

I don't know? I have no idea what you're trying to say there.

To give you an example of recursion: (that incidentally
doesn't do what you'ld expect)

#include <iostream>

void recursion(int n)
{
std::cout << "n = ";
std::cout << n << std::endl;
if(n < 10)
recursion(++n);
}

int main()
{
recursion(0); // prints 11 times
}

And your point is?

Any iterative algorithm can be rewritten to use recursion. Some
languages don't even have looping constructions, but in C++,
using recursion to simluate iteration is poor programming
practice. On the other hand, recursion is considerably more
powerful than iteration, and not all recursive algorithms can be
rewritten in terms of pure iteration, unless you introduce a
manually managed stack, which is a lot more work for the
programmer, and typically less efficient in terms of run-time.
How would you do a depth first visit of a tree without
recursion, for example? (Or quick sort, for that matter? The
standard non-recursive iteration requires a user managed stack.)

Note that recursion is typically less efficient in terms of
memory than managing the stack yourself, so you'll normally want
to avoid recursing too deeply.

--
James Kanze (GABI Software) email:ja******* **@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientier ter Datenverarbeitu ng
9 place Sémard, 78210 St.-Cyr-l'École, France, [phone]

[talk2saber]

On Jan 6, 6:37*pm, James Kanze <james.ka...@gm ail.comwrote:

On Jan 5, 9:19 pm, Salt_Peter <pj_h...@yahoo. comwrote:

On Jan 5, 2:17 pm, "athar.mir...@g mail.com"
<athar.mir...@g mail.comwrote:

.plz define it.

As the English word suggests: a recursion is simply a function
that calls itself. *Which is neither efficient nor beneficial.

It's beneficial when its beneficial. *On most modern
architectures, it's often as efficient as the alternatives. *(I
once benchmarked a recursive version of quick sort, and one
which avoided recursion. *the recursive version was faster.)

Each call generates a new local stack which eventually all
need to be unwound. *So in C++, its usually replaced with
better alternatives. *An example of a preferred alternative
would then be a function object (functor).

How is that relevant to recursion. *A functional object is still
a function, and can still be recursive or not, according to how
you write it.

Recursive functions have no state (what does that mean?).

I don't know? *I have no idea what you're trying to say there.

To give you an example of recursion: (that incidentally
doesn't do what you'ld expect)
#include <iostream>
void recursion(int n)
{
* std::cout << "n = ";
* std::cout << n << std::endl;
* if(n < 10)
* * recursion(++n);
}
int main()
{
* recursion(0); // prints 11 times
}

And your point is?

Any iterative algorithm can be rewritten to use recursion. *Some
languages don't even have looping constructions, but in C++,
using recursion to simluate iteration is poor programming
practice. *On the other hand, recursion is considerably more
powerful than iteration, and not all recursive algorithms can be
rewritten in terms of pure iteration, unless you introduce a
manually managed stack, which is a lot more work for the
programmer, and typically less efficient in terms of run-time.
How would you do a depth first visit of a tree without
recursion, for example? *(Or quick sort, for that matter? *The
standard non-recursive iteration requires a user managed stack.)

Note that recursion is typically less efficient in terms of
memory than managing the stack yourself, so you'll normally want
to avoid recursing too deeply.

--
James Kanze (GABI Software) * * * * * * email:james.ka. [e-mail]
Conseils en informatique orientée objet/
* * * * * * * * * *Beratung in objektorientier ter Datenverarbeitu ng
9 place Sémard, 78210 St.-Cyr-l'École, France, [phone]

I need some memory related information about recursion.
That is how it is implemented

[red floyd]

ta********@gmai l.com wrote:

>
I need some memory related information about recursion.
That is how it is implemented

You answer is found here:

http://www.parashift.com/c++-faq-lit...t.html#faq-5.2