Programming Forums > Application Development > C++

kruptof · Nov 15th, 2006, 12:14 PM

is it possible to know how many elements in an array by just having access to the first elemnt of the array. For example the following code sorts through an array (int) into order, but at the current moment the sorting function relys on the caller passing it the number of elements, so i was just wondering if this can be done by just having access to the first element. thanks

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void sort_array(int* backup,int n)
{
	int * point=backup;

	for(int i=0;i<n;i++)
	{
		point=backup;
		for(int j=i;j<n;j++)
		{
			if(*backup >= *point)
			{
				int temp = *backup;
				*backup = *point;
				*point=temp;
			}
			point++;
		}
		backup++;
	}
}

void main(void)
{
	int lst[11]={7,6,3,4,9,18,1,5,2,2};
	int array_size=(sizeof(lst)/4)-1;
	sort_array(lst,array_size);

	for(int i=0;i<10;i++)
	{
		cout<<lst[i]<<endl;
	}
}

Seif · Nov 15th, 2006, 2:49 PM

Not really, If i were you i'd either use a vector instead of an array. However if you wanted to be dirty about it, you can use exception handling to catch when the end of an array is over reached

Narue · Nov 15th, 2006, 3:04 PM

>is it possible to know how many elements in an array by just having access to the first elemnt of the array.
No, not in a generic way. You need some method of finding the end of the array, whether it be with an item count or a sentinel, or some other trick.

>but at the current moment the sorting function relys on the caller passing it the number of elements
What's wrong with that? The caller is in a much better position to know how many elements are in the array than your function. It's not like the argument has a prohibitive overhead either.

>you can use exception handling to catch when the end of an array is over reached
And what standard exception does an out of bounds access throw in C++?

kruptof · Nov 15th, 2006, 4:29 PM

there is nothing with the caller providing the sentinel but i was just wonedring if it was really possible.........well atleast i know the answer know...thanks

Nov 15th, 2006, 3:04 PM	#3
Narue Professional Programmer Join Date: Sep 2005 Posts: 419 Rep Power: 4	>is it possible to know how many elements in an array by just having access to the first elemnt of the array. No, not in a generic way. You need some method of finding the end of the array, whether it be with an item count or a sentinel, or some other trick. >but at the current moment the sorting function relys on the caller passing it the number of elements What's wrong with that? The caller is in a much better position to know how many elements are in the array than your function. It's not like the argument has a prohibitive overhead either. >you can use exception handling to catch when the end of an array is over reached And what standard exception does an out of bounds access throw in C++? __________________ Even if the voices aren't real, they have some pretty good ideas.

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Nov 15th, 2006, 2:49 PM	#2
Seif Hobbyist Programmer Join Date: Jan 2006 Location: UK Posts: 244 Rep Power: 3	Not really, If i were you i'd either use a vector instead of an array. However if you wanted to be dirty about it, you can use exception handling to catch when the end of an array is over reached

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Programming Forums > Application Development > C++

Finding n element of array