Home/ Questions/Can I fix the “c++ expression must have a constant value” or not?
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Lyra Lee
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Asked: 2022-05-18T20:59:42+00:00 In:

Can I fix the “c++ expression must have a constant value” or not?

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I’m building a new program, but when I run it, an error pops up. The error displayed is as follows:

expression must have a constant value

I have tried several workarounds, but they still do not get the desired results. If you have come across this situation and have a solution for the “c++ expression must have a constant value” problem, pls let me know. Here is what I do:

int row = 8;
 int col= 8;
 int [row][col];

Thanks!

c++ expression must have a constant value
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2 Answers

  1. Best Answer
    Expert

    The cause:

    I found that you attempted to set size of an array to values which are not constant. However, C++ does not accept these non-constant values, so the error: ”c++ expression must have a constant value” happens.

    Solution:

    Let’s follow this simple way to fix your error:

    const int row = 8;
const int col= 8;
int a[row][col];

    UPD: You can actually accomplish this with some compilers. I believe g++ contains this function, but you should not use it because your code will not be movable to the other compilers.

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  2. An array such as this must have a constant size. You will need to allocate memory on the heap to create a dynamic array. After you are done, you can also free it with delete 

    //allocate the array
int** arr = new int*[row];
for(int i = 0; i < row; i++)
 arr[i] = new int[col];

// use the array

//deallocate the array
for(int i = 0; i < row; i++)
 delete[] arr[i];
delete[] arr;

    You must declare const. 

    const int row = 8;
const int col = 8;
int arr[row][col];

    Also, 

    int [row][col];

    does not even include a variable name.

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