Declaring an array outside and initializing using an initialize list

Question

I am having trouble initializing a 2D int array. The structure of my program is:

int arr[2][2];
if(val==1)
 arr = {{1,1}, {2,2}};
else if (val==2)
 arr = {{3,3}, {4,4}};
...
...

int x = arr[1][1];
...

I am getting an error "Expression must be a modifiable lvalue"

Thanks.

@ArchLinuxTux do you believe the accepted answer here is a duplicate of the answer of your question? I fail to see how they are duplicates. The accepted answer of using array<> is the right way to go about this and it was not part that answer. — madu
– madu, Commented Mar 19, 2018 at 7:15
@madu It's no duplicate, because the other answer is in C and the solution from C doesn't work for C++. — aiutopia.dev
– aiutopia.dev, Commented Mar 19, 2018 at 14:41
If someone needs to do this in C, here is how with this one: char (*daytab)[3] = (char [][3]){{1, 31, 4}, {2, 31, 4}}; for multidimensional arrays. — aiutopia.dev
– aiutopia.dev, Commented Mar 21, 2018 at 7:36
@madu (I am grown-up ArchLinuxTux) i just sometimes click the duplicate question button and then stackoverflow auto-generates these comments... — aiutopia.dev
– aiutopia.dev, Commented Dec 31, 2024 at 14:27

dontpanic · Accepted Answer · 2018-03-19 06:55:48Z

7

In your code, arr = {{1,1}, {2,2}}; is not initialization. If you insist on the native array, I'm afraid you have to manually set each element.

However you can switch to use std::array, which gives what you want:

array<array<int, 2>, 2> arr;
if (val == 1)
    arr = { { { 1,1 }, { 2,2 } } };
else if (val == 2)
    arr = { { { 3,3 }, { 4,4 } } };

int x = arr[1][1];

Note the extra braces (see here).

answered Mar 19, 2018 at 6:55

dontpanic

3512 silver badges8 bronze badges

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

1 Comment

aiutopia.dev Over a year ago

with c++14 extra-braces are not needed anymore.

Beyondo · Accepted Answer · 2018-03-19 21:27:29Z

3

Initializing

int arr[2][2] = {{3,3}, {4,4}};

modifying

arr[0][0] = 3;
arr[0][1] = 3;
arr[1][0] = 4;
arr[1][1] = 4;

edited Mar 19, 2018 at 21:27

answered Mar 19, 2018 at 6:58

Beyondo

3,3381 gold badge20 silver badges46 bronze badges

2 Comments

madu Over a year ago

Thank you. This is not quiet possible because arr is actually a [10][11] array.

Beyondo Over a year ago

this is the way for int types, you're still able to loop and make things easier, or since you mentioned C++, things are more comfortable with its provided libraries.

Collectives™ on Stack Overflow

Declaring an array outside and initializing using an initialize list

2 Answers 2

1 Comment

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related