C struct within a struct hardcoded initialization

Question

What I am doing wrong here for C99:

struct chess {
    struct coordinate {
        char piece;
        int alive;
    } pos[3];
}table[3] =
{
    {
      {'Q', (int)1},{'Q', (int)1},{'Q', (int)1},
      {'B', (int)1},{'B', (int)1},{'B', (int)1},
      {'K', (int)1},{'K', (int)1},{'K', (int)1},
    }
};

It gives the error:

error: expected ‘:’, ‘,’, ‘;’, ‘}’ or ‘__attribute__’ before ‘=’ token

I wish to be able to access the data like having a struct within a struct that:

table[row].pos[column].piece
table[row].pos[column].alive

I tried several combinations, and none seems to work for this case. I have done previous struct hard coded initialization before that works, but not a struct within a struct as this time.

Any suggestions?

Please read your error messages; I'm pretty sure your compiler would have told you it cannot convert a `char *` to a `char`, which would tell you exactly what your problem is. — Ken Y-N, Oct 31 '16 at 08:39
And there is no need to cast 1 to int as it is already of that type. — 2501, Oct 31 '16 at 08:41

score 5 · Answer 1 · edited Oct 31 '16 at 09:14

5

Try to enclose char literals in single quotes as stated above and add extra braces to make inner arrays to be initializer lists.

struct chess
{
   struct coordinate
   {
       char piece;
       int alive;
   } pos[3];
}
table[3] =
{  // table of 3 struct chess instances...
   { // ... start of a struct chess with a single member of coordinate[3]...
      { // ... this is where the  coordinate[3] array starts... 
         // ... and those are the individual elements of the  coordinate[3] array
         {'Q', 1}, {'Q', 1}, {'Q', 1}
       }
    },
    {{{'B', 1}, {'B', 1}, {'B', 1}}},
    {{{'K', 1}, {'K', 1}, {'K', 1}}}
};

edited Oct 31 '16 at 09:14

Adrian Colomitchi

3,974
1
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answered Oct 31 '16 at 08:46

lost_guadelenn

447
4
14

Can you please advice why is there double `{{}}` around raw? – Peter K. Oct 31 '16 at 08:53
Well, I think this is how it works: table[3] = { // init list of table[] { // init list of struct chess { // init list of pos[] {'Q', 1}, // init list of coordinate } }, {{{'B', 1}, {'B', 1}, {'B', 1}}}, {{{'K', 1}, {'K', 1}, {'K', 1}}} }; Check the following url for more examples: http://en.cppreference.com/w/c/language/struct_initialization – lost_guadelenn Oct 31 '16 at 09:07

score 4 · Accepted Answer · 2016-10-31T09:19:30.110

struct chess {
    struct coordinate {
        char piece;
        int alive;
    } pos[3];
} table[3] =
{
    {
        .pos = {{ .piece = 'Q', .alive = 1 },
                { .piece = 'Q', .alive = 1 },
                { .piece = 'Q', .alive = 1 }
               }
    },
    {
        .pos = {{ .piece = 'B', .alive = 1 },
                { .piece = 'B', .alive = 1 },
                { .piece = 'B', .alive = 1 }
               }
    },
    {
        .pos = {{ .piece = 'K', .alive = 1 },
                { .piece = 'K', .alive = 1 },
                { .piece = 'K', .alive = 1 }
               }
    }
};

It seems to work. Just be careful about the placement of your braces, and PLEASE try to understand what you are typing. This is how to read the answer :

table[3] is an array. So the initializer begin by '{' and ends by '};', with each element separated by a ','
each element of this array is a 'struct chess'. So each sub-element begins by '{' and ends by '}'
in each 'struct chess' you have an array 'pos[3]'. So another sub-sub '{' and '}'
each 'pos' is a struct, so there is sub-sub-sub '{' and '}'
finally, the fields are here. Use the C99 initializer list to make your code cleaner. And double quotes in C are char*, not char. Use single-quotes

Advices :

try to minimize the amount of "difficult-to-read" code. It will serve you
I never use nested structs. When needed, separate their codes and create function which will initialize them.
CPPReference is useful
use good variables name and identifiers for your struct. When i read 'pos', I think it is a position on a chess ((x, y) coordinates with informations).

C struct within a struct hardcoded initialization

2 Answers2