How do I get a count of the values in a array?

[gk245]

For instance, if i had a array like this:

array[] = {1, 2, 3, 5, 6, ......};

How do i tell C go get me the number of values in the array? Not the
value itself, but how MANY of them there are.

Thanks, please don't give me anything fancy. Since i can't use other
functions to give that answer, just for loops and such.

 

[Ben Pfaff]

For instance, if i had a array like this:

array[] = {1, 2, 3, 5, 6, ......};

How do i tell C go get me the number of values in the array? Not the
value itself, but how MANY of them there are.

sizeof array / sizeof *array

(This will work only for an actual array, not for a pointer into
an array.)

 

[gk245]

Ben Pfaff wrote on 3/16/2006 :

For instance, if i had a array like this:

array[] = {1, 2, 3, 5, 6, ......};

How do i tell C go get me the number of values in the array? Not the
value itself, but how MANY of them there are.

sizeof array / sizeof *array

(This will work only for an actual array, not for a pointer into
an array.)

Thx, but like i said, i can't use a function to do this. sizeof is a
function, right?

 

[Ben Pfaff]

sizeof is a function, right?

No. sizeof is an operator.

 

[gk245]

Ben Pfaff wrote on 3/16/2006 :

No. sizeof is an operator.

lol, sorry. Yeah, unfortunately can't use that either. Haven't
covered it yet.

 

[David Resnick]

Ben Pfaff wrote on 3/16/2006 :

lol, sorry. Yeah, unfortunately can't use that either. Haven't
covered it yet.

Put a sentinel value at the end that isn't a legal value. For example,
if your
array can only contain non-negative integers, put -1 at the end. If it
can
only contain non-null pointers, put NULL at the end. etc.

-David

 

[Kenneth Brody]

Ben Pfaff wrote on 3/16/2006 :

lol, sorry. Yeah, unfortunately can't use that either. Haven't
covered it yet.

Translation:

This is a homework assignment, and we aren't allowed to use anything
we haven't covered yet in class.

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+-------------------------+--------------------+-----------------------------+
Don't e-mail me at: <mailto:[email protected]>

 

[Ben Pfaff]

Ben Pfaff wrote on 3/16/2006 :

lol, sorry. Yeah, unfortunately can't use that either. Haven't
covered it yet.

Then use a macro:
#define ELEM_CNT 5
int array[ELEM_CNT] = {1, 2, 3, 4, 5};
Thereafter, just use ELEM_CNT as the number of elements in the
array.

 

[Martin Ambuhl]

For instance, if i had a array like this:

array[] = {1, 2, 3, 5, 6, ......};

How do i tell C go get me the number of values in the array? Not the
value itself, but how MANY of them there are.

int main(void)
{
int array[] = {1, 2, 3, 5, 6};
size_t nelements = sizeof array / sizeof *array;
return 0;
}

 

[Martin Ambuhl]

Thx, but like i said, i can't use a function to do this. sizeof is a
function, right?

NO. Please open your damn C text. Start at page one.

 

[gk245]

Martin Ambuhl wrote :

NO. Please open your damn C text. Start at page one.

take it easy man. I had forgotten since there is quite a lot to learn
in the beginning.

 

[CBFalconer]

Ben Pfaff wrote on 3/16/2006 :

lol, sorry. Yeah, unfortunately can't use that either. Haven't
covered it yet.

Then you have no way. So go ahead and use it. That's why it is in
the language.

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[Guest]

the numbers in an array is equal to:

sizeof(array)/sizeof(array[0])

for example:

main()
{
float array[]={3.14,-9.21,1.7e2,-99,0.12};

printf("%d\n",sizeof(array)/sizeof(array[0]));
}

 

[Richard Bos]

Then you have no way.

Actually, I believe that since we already have a well-defined array to
apply this to, as well as well-defined members of this array, there is a
way to do this. It is, however, not something a beginning student should
even attempt, since it's likely to teach bad habits.

Richard

 

[Robben]

I guess this could be an interview question to test your knowledge of
C. For Arrays in C there is no way to find the count of the number of
elements of an array without using sizeof operator.

If you use a for loop you need to know the size earlier as C allows to
access the elements beyond the maximum array length; and it can fall
into an infinite loop.

 

[Keith Thompson]

For instance, if i had a array like this:

array[] = {1, 2, 3, 5, 6, ......};

How do i tell C go get me the number of values in the array? Not the
value itself, but how MANY of them there are.

Thanks, please don't give me anything fancy. Since i can't use other
functions to give that answer, just for loops and such.

I guess this could be an interview question to test your knowledge of
C. For Arrays in C there is no way to find the count of the number of
elements of an array without using sizeof operator.

If you use a for loop you need to know the size earlier as C allows to
access the elements beyond the maximum array length; and it can fall
into an infinite loop.

Robben, please don't top-post. I've corrected it here.

Actually, there are ways to compute the size of an array without using
sizeof. They involve some ugly pointer arithmetic and casts to char*.
I'm not going to go into details because (a) the OP didn't want
anything fancy, and (b) there's no good reason not to use sizeof.

 

[Barry Schwarz]

I guess this could be an interview question to test your knowledge of
C. For Arrays in C there is no way to find the count of the number of
elements of an array without using sizeof operator.

If you use a for loop you need to know the size earlier as C allows to
access the elements beyond the maximum array length; and it can fall
into an infinite loop.

While accessing an element beyond the maximum array length need not be
a syntax error, C does NOT allow it. Any attempt to do so invokes
undefined behavior and you have left the C universe for parts unknown.

For instance, if i had a array like this:

array[] = {1, 2, 3, 5, 6, ......};

How do i tell C go get me the number of values in the array? Not the
value itself, but how MANY of them there are.

Thanks, please don't give me anything fancy. Since i can't use other
functions to give that answer, just for loops and such.

Remove del for email

 

[Dave Thompson]

For instance, if i had a array like this:

array[] = {1, 2, 3, 5, 6, ......};

How do i tell C go get me the number of values in the array? Not the
value itself, but how MANY of them there are.

sizeof array / sizeof *array

(This will work only for an actual array, not for a pointer into
an array.)

Correct, but I think it is worth noting explicitly a consequence of
this that people (too) often miss:

And if you (try to) declare function's (formal) parameter as an array,
it is actually 'adjusted' to a pointer, and this method doesn't work.

- David.Thompson1 at worldnet.att.net