recursion.

[pereges]

AS I understand, there must be a stopping condition in recursive
functions.

suppose my function is like this -

void build_kdtree(kd node *kd, int axis, int depth)
{

if(kd->maxspheres <= MINSPHERES || depth >= DEPTHLIMIT)
{
kd->left = kd->right = NULL;

}

else
{

,,,,,,,,

build_kdtree(kd->left, axis, depth+1);
build_kdtree(kd->right, axis, depth+1);

}

My question is -

1. Is the stopping condition in if sufficient or some return value is
also necessary
2. Is this a right way to build a recursive function ?

[Chris Dollin]

Re: recursion.

pereges wrote:

AS I understand, there must be a stopping condition in recursive
functions.

In a non-lazy language like C, yes.

suppose my function is like this -
>
void build_kdtree(kd node *kd, int axis, int depth)
{
>
if(kd->maxspheres <= MINSPHERES || depth >= DEPTHLIMIT)
{
kd->left = kd->right = NULL;
>
}
>
else
{
>
,,,,,,,,
>
build_kdtree(kd->left, axis, depth+1);
build_kdtree(kd->right, axis, depth+1);
>
}
>
My question is -
>
1. Is the stopping condition in if sufficient or some return value is
also necessary

You don't need a return value "just because" the function's recursive.

2. Is this a right way to build a recursive function ?

Looks plausible; can't tell without knowing more about the domain.

--
"Some of these", Hazleton had said, looking at a /A Clash of Cymbals/
just-completed tangle of wires, lenses, antennae and
kernels of metal with rueful respect, "ought to prove pretty potent in the
pinch. I just wish I knew which ones they were."

Hewlett-Packard Limited registered office: Cain Road, Bracknell,
registered no: 690597 England Berks RG12 1HN

[pereges]

Re: recursion.

On Apr 9, 5:51 pm, Chris Dollin <chris.dol...@h p.comwrote:

2. Is this a right way to build a recursive function ?

>
Looks plausible; can't tell without knowing more about the domain.

Well, kdtree is a binary tree where every node has a left child and
right child. IF I was making a recursive program for binary tree, then
if the stopping condition is satisfied what should I do ? I would make
the left and right child of this node null as it is a leaf node. but i
was wondering if this was sufficient as i have seen quite a few
recursive programs which do return a value.

[Chris Dollin]

Re: recursion.

pereges wrote:

On Apr 9, 5:51 pm, Chris Dollin <chris.dol...@h p.comwrote:
>

2. Is this a right way to build a recursive function ?

>>
>Looks plausible; can't tell without knowing more about the domain.

>
Well, kdtree is a binary tree where every node has a left child and
right child. IF I was making a recursive program for binary tree, then
if the stopping condition is satisfied what should I do ?

The right thing -- whatever that is. There are many different
recursive programs on binary trees, so without knowing more
about what problem you're solving it's hard to be more specific.

I would make
the left and right child of this node null as it is a leaf node. but i
was wondering if this was sufficient as i have seen quite a few
recursive programs which do return a value.

Your function is called `build_kdtree`, but it appears to traverse
an existing tree, and the interesting stuff is buried in the elipsis
",,,,,,,,". So I'm confused.

You return a value if you need a value returned, and not if you
don't.

(fx:google) Ah, I find a definition of kd-tree. Don't you need
some points to construct the tree over, and not just a deph & axis?

--
"Its flagships were suns, its smallest vessels, /The City and the Stars/
planets."

Hewlett-Packard Limited Cain Road, Bracknell, registered no:
registered office: Berks RG12 1HN 690597 England

[Ben Bacarisse]

Re: recursion.

pereges <Broli00@gmail. comwrites:

On Apr 9, 5:51 pm, Chris Dollin <chris.dol...@h p.comwrote:
>

2. Is this a right way to build a recursive function ?

>>
>Looks plausible; can't tell without knowing more about the domain.

>
Well, kdtree is a binary tree where every node has a left child and
right child. IF I was making a recursive program for binary tree, then
if the stopping condition is satisfied what should I do ? I would make
the left and right child of this node null as it is a leaf node. but i
was wondering if this was sufficient as i have seen quite a few
recursive programs which do return a value.

That is cargo cult programming[1]. You are in charge -- it is your
program. You decide if you need a value and if so what. If you don't
need one, don't have one!

Also, rather than ask: "if the stopping condition is satisfied what
should I do?" you should ask "what is the recursive algorithm for
building such-and-such a type of tree?". You start with the
algorithm. When you understand that, what to do in various situation
will be clearer. Without the algorithm, no one can answer you
question.

[1] http://en.wikipedia.org/wiki/Cargo_cult_programming

--
Ben.