warning: comparison between pointer and integer

lxmirmsh · 05-02-2013, 12:13 PM

struct node
{
char prod[20];
struct node *lt,*rt;
}*n;

void display(struct node *root,int h)
{
int i;
if(root!=NULL)
{
display(root->rt,h+1);
for(i=0;i<n;i++)
printf("\t");
printf("%s",root->prod)
display(root->lt,h+1);
}
}

this is just a part of the code. when i run the code i get this
" warning: comparison between pointer and integer [enabled by default]" line number 13

mlslk31 · 05-02-2013, 01:54 PM

You've declared n to be a pointer of type "struct node" and i as an int, so there's a comparison between pointer and integer.

lxmirmsh · 05-02-2013, 02:35 PM

How do i correct it?

johnsfine · 05-02-2013, 02:41 PM

Quote:

Originally Posted by lxmirmsh

for(i=0;i<n;i++)

Did you write this code?
If so, what did you intend i<n to mean?

You have n declared as a pointer to a struct, not as a number, so the use of n in that for statement makes no sense.

If you copied code from someone else, I think you missed a declaration of n in the current scope.

mlslk31 · 05-02-2013, 03:02 PM

You correct it by doing something else useful with the struct. Access one of its members, or get the address of the struct. One of the few things that might be useful with just n is to compare it to another "struct node", but to compare it to an integer that starts with 0 might not be what you want. Or is it? This is why my previous answer was so short.

For a lot of things in C, you can cast from one type to another, as in this:

Code:

n = (struct node *)malloc( sizeof( struct node ));

This doesn't seem to be one of those times.

bloody · 05-02-2013, 03:30 PM

That for loop is strange:

Code:

for(i=0;i<n;i++)

This thing would repeatedly print one tabulator character.
To make this fact more clearly visible, i would really suggest to indent the following printf-line, as this will be the only thing that would be executed as body of the for() loop.

And then, how many TAB characters do you intend to print?

You probably want to remove the for() line entirely?

bloody · 05-02-2013, 03:34 PM

Addendum: maybe "h" means "number of horizontal tabulators"? Then you should replace that "i<n" with "i<h", as "h" is not used anywhere else in the code? Anyhow, strange code snippet.

johnsfine · 05-02-2013, 06:23 PM

Quote:

Originally Posted by bloody

you should replace that "i<n" with "i<h"

You are correct. I didn't look at the OP's code carefully enough the first time to see that.

Quote:

maybe "h" means "number of horizontal tabulators"?

h represents how many levels of the sideways tree being printed are to the left of the subtree currently being printed. It is a recursive tree printing routine. That is what I didn't pay attention to the first time. So for the actual printing at each level (the part other than the recursion), you need h tabs to the left of the text.

lxmirmsh · 05-03-2013, 11:03 AM

@johnsfine

No, i did not write the code on my own. i did try n replace "n" with "h", still gives me a warning

lxmirmsh · 05-03-2013, 11:06 AM

@mlslk31

the allocation is made elsewhere, and yes it dint make sense to me either:/

johnsfine · 05-03-2013, 11:48 AM

Quote:

Originally Posted by lxmirmsh

No, i did not write the code on my own. i did try n replace "n" with "h", still gives me a warning

That was supposed to be change just the n in i<n to h. Any other n was probably correct.

I don't see how that could give the same warning. Maybe you forgot to save the edit and recompiled the earlier version again.

What line is the warning on (and if it is a different warning, what is the warning)?

lxmirmsh · 05-04-2013, 10:14 AM

yeah I did change the "n" to "h" only in i<n and no, it does not give the same warning.
when I replace n with h, I get this - "warning: assignment from incompatible pointer type [enabled by default] "

johnsfine · 05-05-2013, 05:27 AM

Quote:

Originally Posted by lxmirmsh

yeah I did change the "n" to "h" only in i<n and no, it does not give the same warning.

So you fixed that problem and you have some other problem.

Quote:

I get this - "warning: assignment from incompatible pointer type [enabled by default] "

A warning message like that includes the line number of the source line that caused the warning.

For someone to help you, you must post source code including the line the warning complained about, and you must identify which line it was.

lxmirmsh · 06-03-2013, 11:38 AM

Thank you all for your help!
The warning is removed. yes, all i had to do was to replace "n" with "h". When i replaced it last time, I'd made a typing mistake elsewhere. Thats's why i got a warning.