For Loop not executing

Question

The formula simply isn't executing. I tried using printf to debug and it printed out 0 for i at the end of the code

#include <stdio.h>

int main()
{
 int i, base, height;
 printf("Lumber  Cross-Sectional   Moment of Section\n");
 printf("Size  Area    Inertia  Modulus\n");
 for (i = 0; i > 35; i++)
 {
  if (i == 6 || i == 12 || i == 18|| i == 24 || i == 30)
  {
   base = base * 2;
   height = 2;
  }
  if (i != 6 || i != 12 || i != 18 || i != 24 || i != 30)
  {
   height = height * 2;
  }
  printf("%d x %d %d  %d   %d \n", base, height, base * height, base * 2 + height); 

 }//for  
 return (0);
}//main

Another bug -- don't assume base=0 and height=0 at the beginning of the loop. They could be anything. — Vladimir Dyuzhev
– Vladimir Dyuzhev, Commented Jul 10, 2010 at 2:02
Looking at your other questions, you seem to not understand how certain constructs work, and you don't know how to use a debugger (for stepping through code, checking variable values and showing you how it skips over the loop). — Radu C
– Radu C, Commented Jul 10, 2010 at 14:07

Bill the Lizard · Accepted Answer · 2010-07-10 01:56:18Z

17

Should be

for (i = 0; i < 35; i++)

The body of the loop will only execute when the condition is true.

answered Jul 10, 2010 at 1:56

Bill the Lizard

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txwikinger · Accepted Answer · 2010-07-10 01:59:57Z

4

It should be

for (i = 0; i < 35; i++)

as said by Bill the Lizard.

for (i = 0; i > 35; i++)

is never true in its condition since 0 < 35 and hence the loop body is never executed.

answered Jul 10, 2010 at 1:59

txwikinger

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Comments

Alok Singhal · Accepted Answer · 2010-07-10 16:48:38Z

You need to think what your conditions mean. The reason the loop doesn't execute is mentioned by others. Let's look at the other condition:

if (i != 6 || i != 12 || i != 18 || i != 24 || i != 30)

When do you think the above condition will be false? We need to look at two cases:

i is equal to 6. So, i != 6 is false, but every other part of the condition (i != 12, etc.) is true. This is because 6 is only equal to 6, and no other number. So the overall condition is true.
i is not equal to 6. Now, i != 6 is true, and therefore the whole condition is true.

So, your if condition above is always true.

Also, think about what would happen if you were looping till a large number, let's say 215. Will you want to have a condition like:

if (i == 6 || i == 12 || ... || i == 210)

Surely, there has to be a better to do what you want. I think what you want is to multiply base by 2, and reset height when i is divisible by 6; otherwise multiply height by 2. The code structure becomes:

/* not legal C */
if (i is divisible by 6) {
} else {
}

To test divisibility by 6, remember that for numbers n and m, n % m gives you the remainder of n divided by m.

d3vdpro · Accepted Answer · 2010-07-10 02:52:37Z

0

As said by the above two mates for loop will not execute until the condition is true. Before asking it here you should have debugged it yourself. :)

answered Jul 10, 2010 at 2:52

d3vdpro

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Praveen S · Accepted Answer · 2010-07-10 07:14:43Z

0

I think if you reshape the code and the conditions, it will be lot better. Can you change the for loop to for (i=1 ; i<36 ; i++)? This way you can simplify the if condition inside the loop,as you can see you are checking if its a multiple of 6 in the code. You can just think on those lines.

Some more pointers:

Initialize all variables to default values.
Print the output in better readable way. Delete x from it. Also space the values equally using \t.

answered Jul 10, 2010 at 7:14

Praveen S

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Comments

chaitanyavarma · Accepted Answer · 2010-07-10 13:23:50Z

0

The first loop will never execute.First time for checks for the (i>35), in your case i<35, so the loop will not execute.

answered Jul 10, 2010 at 13:23

chaitanyavarma

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