getting array size

[Cosizzle]

Hey guys,

Sorry for the simplistic question, I come from a PHP/Java background.

What im trying to figure out is how I can find out the array size of an array being passed into a class function.

so:

int cmds[] = {5,5,4,5,9,2}
...
turtleOne.processTurtleMoves(cmds);

=====[in the class now]=====
void TurtleGraphics:: processTurtleMoves(const int commands[])
{
// how would I get the size here (6)
// my understanding is that I should be able to go:
cout << sizeof commands / sizeof(int);
// however I get 1 as a result. Is this because of the constant?
}

Thank you kindly for your help!
-Cody

[Cosizzle]

sorry, I should be more specific - I'm looking for the array length.

[ZuK]

The reason why that doesn't work is that you cannot pass arrays to functions. You're only passing a pointer to it's first element.
But then why do you want to calculate the size of an arry ?. You know the size whan you create it..
And yes you have to pass that size to any functions that uses the array as an additional parameter.

Kurt

[Cosizzle]

Thank you for your reply.

I don't know the size when I create it because I'm not specifying a size - it's dynamic. In my example it's 6.. in my application its about 50 give or take.

Why I need to calculate the length of the array is because each number in that array needs to do something. Therefore I need to loop through it, and within the loop create a switch statement that checks the current number and performs actions based on the case.

[ZuK]

Originally Posted by Cosizzle

I don't know the size when I create it because I'm not specifying a size - it's dynamic. In my example it's 6..

Shure you know. You just said it's 6 in that example.

Kurt

[Cosizzle]

Yes... but that number could change, so opposed to hard coding that number in is there any way to have it dynamic.

[ZuK]

Originally Posted by Cosizzle

Yes... but that number could change, so opposed to hard coding that number in is there any way to have it dynamic.

There isn't anything like a dynamic array in c++. ( ok a std::vector is ).

You could do something like this

int cmds[] = {5,5,4,5,9,2};
int num_cmds = sizeof(cmds) / sizeof(cmds[0]) ;

But that works only as long as cmds is an array. If you pass cmds to a function it becomes a pointer.
Kurt

[Lindley]

The bottom line is that you can always know the array size at the point of creation, but it's necessary to pass that information around along with the array when using it elsewhere. This can either be done via a separate parameter (which is the common C approach), or by putting both the array pointer and the size into a class object (the C++ approach).

Two such classes are already provided by the C++ standard library: std::tr1::array for fixed-size arrays, and std::vector for dynamic-size arrays.

[cilu]

I suggest you take a look at this article: http://www.codeguru.com/cpp/cpp/cpp_...le.php/c15257/.

[gokmen]

If it is possible, You can send the size of array to called function as a second parameter like:

int cmds[] = {5,5,4,5,9,2}
int size = sizeof(cmds) / sizeof(cmds[0]) ;
...
turtleOne.processTurtleMoves(cmds, size);
.
.
.



void TurtleGraphics::processTurtleMoves(const int commands[], const int size)
{
     cout << size;
}