Doubt in Code

[Priya Mishra]

Hi Everybody

Well I saw one open source code, Which is written in C++ in this code
i came across
very unusall style of coding I am bit fixed on this, please any one
from you all help me.

I am pasting the only refrence code.

MNode *MTree::FindNode(char *nodeName, MNode *startNode)
{
MNode *current=startNode?startNode:root; -----> A
I am not able to understand the why the initialisation of the current
is done in
the above fashion. Both MNode and MTree are the Classes.

where MNode and MTree are the classes, well in the MTree class there is
class MTree
{
public:
MNode *root;
MNode *FindNode(char *nodeName, MNode *startNode = 0);
Thanks and Regards
~Priya

[Erik Wikström]

On 2006-06-10 13:05, Priya Mishra wrote:

Hi Everybody

Well I saw one open source code, Which is written in C++ in this code
i came across
very unusall style of coding I am bit fixed on this, please any one
from you all help me.

I am pasting the only refrence code.

MNode *MTree::FindNode(char *nodeName, MNode *startNode)
{
MNode *current=startNode?startNode:root; -----> A
I am not able to understand the why the initialisation of the current
is done in
the above fashion. Both MNode and MTree are the Classes.

where MNode and MTree are the classes, well in the MTree class there is
class MTree
{
public:
MNode *root;
MNode *FindNode(char *nodeName, MNode *startNode = 0);

I'm not 100% sure I understand your question but I'm making a guess here
that you are talking about why the initialization-line contains the
?:-operator.

The code that initializes current first checks if startNode is a null-
pointer, in which case it sets current to root and startNode if it's not
a null-pointer. I've rewritten the code slightly to make it more readabe:

MNode *current = (startNode ? startNode : root);

This combined with the fact that FindNode has a default-value for the
startNode-parameter makes it easy to search for nodes in the same tree/
graph as root since you can just call FindNode("nodename"); and
startNode will then be a null-pointer which will initialize current to root.

Erik Wikström
--
"I have always wished for my computer to be as easy to use as my
telephone; my wish has come true because I can no longer figure
out how to use my telephone" -- Bjarne Stroustrup

[Jerry Coffin]

In article <1149937533.783298.246130
@h76g2000cwa.googlegroups.com>, mi*******@gmail.com
says...

[ ... ]

MNode *MTree::FindNode(char *nodeName, MNode *startNode)
{
MNode *current=startNode?startNode:root; -----> A

This allows you to tell it where to start the search
from, but if you pass a null pointer, it starts from the
root.

The declaration probably includes NULL as the default
value for the parameter. When you make a call, you just
pass the string you want to look for. It probably
operates recursively, and this avoids having a front-end
function that does nothing but pass the root to the
internal function that does the real searching.

--
Later,
Jerry.

The universe is a figment of its own imagination.