What does this C error about structures mean?

Question

Hey everyone! Could someone please help me understand this error in C for structures? This is my code:

struct Orientation
{
    char facing;
    char sensor;
    char mazeDir;
}; 

struct Orientation O[16];
O[0] = {'N', 'F', 'N'};
O[1] = {'N', 'B', 'S'};
O[2] = {'N', 'R', 'E'};
O[3] = {'N', 'L', 'W'};
O[4] = {'S', 'F', 'S'};
O[5] = {'S', 'B', 'N'};
O[6] = {'S', 'R', 'W'};
O[7] = {'S', 'L', 'E'};
O[8] = {'E', 'F', 'E'};
O[9] = {'E', 'B', 'W'};
O[10] = {'E', 'R', 'S'};
O[11] = {'E', 'L', 'N'};
O[12] = {'W', 'F', 'W'};
O[13] = {'W', 'B', 'E'};
O[14] = {'W', 'R', 'N'};
O[15] = {'W', 'L', 'S'};

and I get these errors regarding O[13], O[14] and O[15]

..\RMNCODE.C(282): error C231: 'O': redefinition
..\RMNCODE.C(283): error C279: 'O': multiple initialization
..\RMNCODE.C(283): error C231: 'O': redefinition
..\RMNCODE.C(284): error C279: 'O': multiple initialization
..\RMNCODE.C(284): error C231: 'O': redefinition

Answer 1

Initialize the array like this instead:

struct Orientation O[16] = {
    {'N', 'F', 'N'},
    {'N', 'B', 'S'},
    {'N', 'R', 'E'},
    {'N', 'L', 'W'},
    {'S', 'F', 'S'},
    {'S', 'B', 'N'},
    {'S', 'R', 'W'},
    {'S', 'L', 'E'},
    {'E', 'F', 'E'},
    {'E', 'B', 'W'},
    {'E', 'R', 'S'},
    {'E', 'L', 'N'},
    {'W', 'F', 'W'},
    {'W', 'B', 'E'},
    {'W', 'R', 'N'},
    {'W', 'L', 'S'}
};

Cheers !

Answer 2

Either you have to initialize O with a single initializer, or you can assign to its members individually in an initialization function. You can't use assignment expressions outside of a function as you have done.

e.g.

struct Orientation O[16] = { {'N', 'F', 'N'}, {'N', 'B', 'S'} /* , ... */ };

or

void InitializeO(void)
{
    O[0].facing = 'N';
    O[0].sensor = 'F';
    O[0].mazeDir = 'N';

    O[1].facing = 'N';
    O[1].sensor = 'B';
    O[1].mazeDir = 'S';

    /* ... */
}

Answer 3

If you're going to initialize O, you need to do it all at once as part of the declaration:

struct Orientation O[16] = {
  { 'N', 'F', 'N' },
  { 'N', 'B', 'S'),
  ...

};

You can't do this:

O[0] = {'N', 'F', 'N'};

because C doesn't support struct literals in a statement, only as part of an initializer list.

Answer 4

You can't assign a struct like you're doing. You need to do it explicitly:

O[0].facing = 'N';
O[0].sensor = 'F';
O[0].mazeDir = 'N';

O[1].facing = 'N';
O[1].sensor = 'B';
O[1].mazeDir = 'S';

//etc...

Or else you can initialize the struct like Magnus suggested.

Answer 5

Change the assignment by an initialization.

struct Orientation { char facing; char sensor; char mazeDir; };

struct Orientation O[16] = 
{{'N', 'F', 'N'},
{'N', 'B', 'S'}, 
{'N', 'R', 'E'}, 
{'N', 'L', 'W'}, 
{'S', 'F', 'S'}, 
{'S', 'B', 'N'}, 
{'S', 'R', 'W'}, 
{'S', 'L', 'E'}, 
{'E', 'F', 'E'}, 
{'E', 'B', 'W'}, 
{'E', 'R', 'S'}, 
{'E', 'L', 'N'}, 
{'W', 'F', 'W'}, 
{'W', 'B', 'E'}, 
{'W', 'R', 'N'}, 
{'W', 'L', 'S'}};

Answer 6

Try

struct Orientation O[16] = {
    { 'W','L','S'},
    { 'W', 'R', 'N'},
    ...
}

Answer 7

Although it is not direct answer to your question, you can solve the problem by following syntax:

struct Orientation O[16] = {
  {'N', 'F', 'N' },
  {'N', 'B', 'S'},
  {'N', 'R', 'E'},
  {'N', 'L', 'W'},
  ...
};

Answer 8

C89 doesn't have literals for structures. It does have initialization lists, which look as if they are literals, but really aren't.

This means that you can only do the "initializing assignment" once, where the variable is defined:

struct Orientation O[16] = {
  {'N', 'F', 'N'},
  ...
};

In C99, this has changed, see the link in the comment.