Thread: Problem with position of variable declaration

Hey guys, I was working on a program to display an output

Code:

1
2    4
3    9    27
4    16    64   256

I got my code working but I noticed something funny...
Here's what the code with var b defined in the inner 'for' loop

Code:

#include <stdio.h>
#include<math.h>

void main(void) {

	double a=1,b;

	for(;a<5;a++)
    {
        for(b=1;b<=a;b++)
        {

        //printf("b is %d\tand a is %d\n",b,a);
            printf("%.0lf\t",pow(a,b));
        }
        printf("\n");

    }
}

The output is as desired in this case...

But when I assign the value of b to the declaration statement like this...

Code:

#include <stdio.h>
#include<math.h>

void main(void) {

	double a=1,b=1;

	for(;a<5;a++)
    {
        for(;b<=a;b++)
        {

        //printf("b is %d\tand a is %d\n",b,a);
            printf("%.0lf\t",pow(a,b));
        }
        printf("\n");

    }
}

I get a wrong output like this (?!)

Code:

1
4
27
256

Oh, and the commented line shows that var b is always zero EVEN though it is incremented in the loop...
Here's the output with that line uncommented and the subsequent line commented...

Code:

b is 0  and a is 1072693248

b is 0  and a is 1073741824

b is 0  and a is 1074266112

b is 0  and a is 1074790400

Thanks in advance for all the help, guys!
Have a great day!

Code:

printf("b is %d\tand a is %d\n",b,a);

Well, to print out double you need to use %lf format specifier.

You need to reinitialize b to 1 for each pass of 1st (a) loop.
I. e.

Code:

double a=1,b=1;
for(;a<5;a++)
{
    for(;b<=a;b++)
    {
        printf("%.0lf\t",pow(a,b));
    }
    printf("\n");
    b = 1;
}

Originally Posted by naaissus

Code:

printf("b is %d\tand a is %d\n",b,a);

Well, to print out double you need to use %lf format specifier.

You need to reinitialize b to 1 for each pass of 1st (a) loop.
I. e.

Code:

double a=1,b=1;
for(;a<5;a++)
{
    for(;b<=a;b++)
    {
        printf("%.0lf\t",pow(a,b));
    }
    printf("\n");
    b = 1;
}

Thanks for the insight provided. I appreciate it greatly.
Quite some embarrassing errors :P
Thanks again!