CODEWITHSUNDEEP
c++
Terik Brunson
Terik Brunson

Reputation: 187

Pointers; Simple Allocation of An Array

I get an error under "int dArray[size]" saying that size needs to be a constant. Can someone explain what that means exactly?

I want it to be an array of size 4 and output 1, 3, 5, and 7.

#include <iostream> 

using namespace std; 

int *AllocateArray(int size, int value){
int dArray[size];
for (int i = 0; i <= size; i++){
    dArray[i] = value;
    value + 2;
}
}

int main(){

AllocateArray(4, 1);
}

Solved:

Here is the code that ended up working.

#include <iostream> 

 using namespace std; 

int *AllocateArray(int size, int value){
int * Array = new int[size];
for (int i = 0; i < size; i++){
    Array[i] = value;
    value = value + 2;
}
for (int i = 0; i < size; i++){
    cout << Array[i] << endl;
}
return Array;
}

int main(){

int *dArray = AllocateArray(4, 1);

}

Upvotes: 0

Views: 56

Answers (4)

imlyc
imlyc

Reputation: 84

The size of array should be a known constant in compile time, so that compiler can allocate correct memory for that array on the stack. Remember that such a declare is for stack variable. If you do want dynamic array, try std::vector.

Upvotes: 1

Thomas Matthews
Thomas Matthews

Reputation: 57678

You have to declare the size of an array using numbers, #define or const unsigned int. Otherwise they are considered variable length arrays.

Example: 

const unsigned int MAX_ARRAY_SIZE = 14;
double my_array[MAX_ARRAY_SIZE];

Upvotes: 0

influxd
influxd

Reputation: 536

C++ requires that the size of arrays are determined at compile-time. As size is determined at runtime, the compiler complains.

If you are interested in having array-like behaviour with a size unknown at compile-time, then consider using std::vector.

Upvotes: 2

NathanOliver
NathanOliver

Reputation: 180424

In int dArray[size] size is not a constant value. Because of that you are getting that error. What you probably wanted to do was make a new array using a pointer and new like:

int * dArray = new int[size];

Upvotes: 3

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