CODEWITHSUNDEEP
cpointersmatrixvoid-pointers
Cyriac Domini Thundathil
Cyriac Domini Thundathil

Reputation: 175

Copy and cast a float matrix into a double matrix using pointers

I have a pointer to a double matrix dmatrix which I declared using: 

double* dmatrix = malloc(n*n*sizeof(double));

I also have a void pointer to a matrix imatrix, which has int values for a matrix of the same dimensions. The int matrix is filled elsewhere in the program. How can I copy the values from imatric to dmatrix using just pointers? This is what I an trying.:

void *a;      
for(int c=0;c<n;c++){
  for(int r=0;r<n;r++){
    a = ((char *)imatrix+(r*n+c)*sizeof(int));
    *(dmatrix+r*n+c) = *(double *)a;
  }
}

Upvotes: 2

Views: 584

Answers (1)

mzu
mzu

Reputation: 723

Wrong. 1. You say imatrix points to int matrix, while you convert it to char*. Why? 2. a is supposedly a pointer in the source matrix. Why do you cast it to (double *)?

I would do something like that:

void* imatrix;
double* dmatrix;

double* p_dmatrix = dmatrix;
int* p_imatrix = imatrix;

for(int i=0; i< r*c; i++)
    *p_dmatrix++ = *p_imatrix++;

Upvotes: 4

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