Cannot Initialize Array with Constant Variable... WHY?

Question

I'm fairly new to programming and I am having trouble initializing an array with a const int. so far for the code I have is this:

int temp = 0;
temp += valuesVec.size();
int SIZE = temp; 
int valuesArray[SIZE];

I am trying to make an array with the same number of elements as a vector that read a file and store all the values. the errors it gives me are:

Error   1   Expected constant expression.
Error   2   error C2466: cannot allocate an array of constant size 0    
Error   3   error C2133: 'valuesArray' : unknown size   
Error   4   IntelliSense: expression must have a constant value

all the errors lead back to: int valuesArray[SIZE]; printing SIZE gave me the value 1118.

I know I am probably doing something stupid and probably forgot some fundamental rule but... Until someone points it out I will be pouring over my book.

Use a std::vector. Use an array only if you have a good reason. — A.B.
– A.B., Commented Nov 12, 2013 at 11:43

Niyaz Ivanov · Accepted Answer · 2013-11-12 05:38:54Z

2

Size of a static array can only be specified with a nonzero constant value. If on the compile time the size is unknown then you should use dynamic array.

int * valuesArray = new int [SIZE];
...
delete[] valuesArray;

Please make sure using proper delete[] operator.

Or better use std::vector

answered Nov 12, 2013 at 5:38

Niyaz Ivanov

6675 silver badges6 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Konrad Rudolph Over a year ago

Remove the new/delete part, it makes this answer worse, not better. It’s error-prone, complicated and not necessary. And it certainly won’t help OP.

Niyaz Ivanov Over a year ago

According to the author's proficiency was given the answer. STL might be confusing for him so far.

Konrad Rudolph Over a year ago

new/delete is more confusing. Despite what people think, the standard library is elementary C++. new/delete is not.

alecbz · Accepted Answer · 2013-11-12 05:40:22Z

0

SIZE is not a compile-time constant (at least not unless valuesVec is), so you can not statically declare an array with SIZE as its size.

You can try manually allocating it:

int* valuesArray = new int[SIZE];

if you remember to delete[] it. Or you can simply make another vector:

std::vector<int> valuesArray(SIZE);

answered Nov 12, 2013 at 5:40

alecbz

6,5684 gold badges34 silver badges52 bronze badges

1 Comment

Konrad Rudolph Over a year ago

Remove the new/delete part, it makes this answer worse, not better. It’s error-prone, complicated and not necessary. And it certainly won’t help OP.

Collectives™ on Stack Overflow

Cannot Initialize Array with Constant Variable... WHY?

2 Answers 2

3 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related