Thread: Question concerning for loops

aside from that, you're still wrong

It's important that you stop being wrong

Originally Posted by Programmer_P

That's BS. Instead of shooting off comments like that, how about presenting some facts, i.e. some proof that you're right, and I'm wrong. How can the statement

Code:

array[ i ] = 10 - i;

be anything but declaring "i" as an element of the array "array", and defining its value?

let me show you

Code:

int main()
{
  int i;

  for ( i = 0; i < 10; i++) {
    printf("array[%d] = %d\n", i, 10 - i);
  }
  
  return 0;
}

^run that code

Originally Posted by Programmer_P

Sorry, changing the code isn't going to help your point any...

I'm showing you what it's actually doing
(HIBT?)

Originally Posted by sean

i is an index used to refer to an element in that array - it is not the element itself. It's a bit like saying that "president is a person". Yes, THE president is a person, but he could be president of anything. It's only when you use that title with a particular context that it refers to an actual entity.

Ok, that makes sense. (That's all I was asking: to prove me wrong with facts, not general statements saying I'm wrong, but not backing it up with facts)
So what the following code

Code:

for ( i = 0; i < 10; ++i )
    {
        array[ i ] = 10 - i;
    }

basically does is goes through all the elements in the array, using a single variable ("i") as reference, and declares each of them as 10 minus the current value of "i" (which changes by 1 each loop). And so the loop body will execute 10 times, and not the 1 like I was originally thinking it would, based on thinking "i" was an actual element of the array, and not just a reference to the elements in the array.
So, after the loop is finished,

array[0] = 10
array[1] = 9
array[2] = 8
array[3] = 7
array[4] = 6
array[5] = 5
array[6] = 4
array[7] = 3
array[8] = 2
array[9] = 1

Originally Posted by Programmer_P

Ok, that makes sense. (That's all I was asking: to prove me wrong with facts, not general statements saying I'm wrong, but not backing it up with facts)
So what the following code

Code:

for ( i = 0; i < 10; ++i )
    {
        array[ i ] = 10 - i;
    }

basically does is goes through all the elements in the array, using a single variable ("i") as reference, and declares each of them as 10 minus the current value of "i" (which changes by 1 each loop). And so the loop body will execute 9 times, and not the 1 like I was originally thinking it would, based on thinking "i" was an actual element of the array, and not just a reference to the elements in the array.

10 times

Originally Posted by ಠ_ಠ

10 times

Right. That was a typo. I meant 10 times, but was thinking of the number of the last element in the array (i.e. 9). But I know it begins at 0, and so yes, the loop body will be executed 10 times, and the 10th time the variable "i" updates, "i" will be set to 10, and the loop wont continue.
Only trouble with that logic is, if the array has 10 elements (0 through 9), and the last one is supposed to be a null character, then why does that code set array[9] (i.e. the tenth element of the array) to value 1? Shouldn't it only go up to element 8 of the array and stop there?
So it should actually be a

Code:

int array[11];

and not a

Code:

int array[10];

or a

Code:

for ( i = 0; i <= 8; ++i; ) 
    {
           array[ i ] = 10 - i;
    }

and not a

Code:

for ( i = 0; i < 10; ++i )
    {
        array[ i ] = 10 - i;
    }

The way they have the array and for loop in the tutorial has the last element (which is supposed to be a NULL character) in the array declared as a 1.

Why is that?

Originally Posted by Programmer_P

Right. That was a typo. I meant 10 times, but was thinking of the number of the last element in the array (i.e. 9). But I know it begins at 0, and so yes, the loop body will be executed 10 times, and the 10th time the variable "i" updates, "i" will be set to 10, and the loop wont continue.
Only trouble with that logic is, if the array has 10 elements (0 through 9), and the last one is supposed to be a null character, then why does that code set array[9] (i.e. the tenth element of the array) to value 1? Shouldn't it only go up to element 8 of the array and stop there?
So it should actually be a

Code:

int array[11];

and not a

Code:

int array[10];

or a

Code:

for ( i = 0; i <= 9; ++i; ) 
    {
           array[ i ] = 10 - i;
    }

and not a

Code:

for ( i = 0; i < 10; ++i )
    {
        array[ i ] = 10 - i;
    }

The way they have the array and for loop in the tutorial has the last element (which is supposed to be a NULL character) in the array declared as a 1.

Why is that?

null characters are for character arrays

Code:

for ( i = 0; i == 9; ++i; ) 
    {
           array[ i ] = 10 - i;
    }

That variant will run exactly ZERO times, since i is not 9 the first time round, so it never enters the loop.

Also, it's only strings that need to have a NUL character at the end.

Your second loop looks great.

--
Mats

Originally Posted by Programmer_P

Ok, that makes sense. (That's all I was asking: to prove me wrong with facts, not general statements saying I'm wrong, but not backing it up with facts)
So what the following code

Code:

for ( i = 0; i < 10; ++i )
    {
        array[ i ] = 10 - i;
    }

basically does is goes through all the elements in the array, using a single variable ("i") as reference, and declares each of them as 10 minus the current value of "i" (which changes by 1 each loop). And so the loop body will execute 10 times, and not the 1 like I was originally thinking it would, based on thinking "i" was an actual element of the array, and not just a reference to the elements in the array.
So, after the loop is finished,

array[0] = 10
array[1] = 9
array[2] = 8
array[3] = 7
array[4] = 6
array[5] = 5
array[6] = 4
array[7] = 3
array[8] = 2
array[9] = 1

did you happen to run the code I told you to run?