Question

this seems to be a simple question, but i cannot get my head around it…

i want to set the elements of an array, based on some conditions, in the most elegant way.

this is my non-compiling pseudo code:

float*array=NULL;
switch(elements) {
  case 1: array={1}; break;
  case 2: array={7, 1}; break;
  case 3: array={3, 2, -1}; break;
  case 4: array={10, 20, 30, 40}; break;
  default:break;
}

the size of the array is limited, so i could do something like ‘float array[16];’ as well, but the problem is obviously assignment in the case-statement.

i really don’t want to do something like:

case 2: array[0]=1; array[1]=2;

my current (clumsy) implementation is:

#define ARRAYCOPY(dest, src) for(int i=0;i<sizeof(src)/sizeof(*src);i++)dest[i]=src[i]
// ...
case 2: do {float*vec={1, 2}; ARRAYCOPY(array, vec); } while(0); break;

i’m using the ARRAYCOPY define, since memcpy() doesn’t seem to work. at least doing

float*vec={1, 2}; memcpy(array, vec, sizeof(vec)/sizeof(*vec);

did not fill any values into array.

i guess there must be a nicer solution?

Answer 1

How about:

float *global[] = {
    NULL,
    (float[]){1},
    (float[]){1, 2},
    (float[]){7, 8, 9},
};


/* ... make sure `elements` is in range */
float *array = global[elements];

EDIT

You’re obviously free to continue using the switch:

switch(elements) {
case 1:
    array = (float[]){1};
    break;
}