Thread: Invalid types 'double*[double]' for array subscript

Hi people I have the error I named the question in the function: (With "here" I comment where the compiler send me the error):

Code:

void ftshifting(matriz filter,int rows,int cols){ 
 
 double r2,c2,tmp1_3,tmp2_4; 
 r2 = (rows+1)/2;  c2 = (cols+1)/2;

 for (int i = 0; i<rows/2; i++){
   for (int k = 0; k<cols/2; k++){
       tmp1_3 = filter[i][k]; 
       filter[i][k] = filter[i+r2][k+c2];  //error
       filter[i+r2][k+c2] = tmp1_3;     //error
       tmp2_4 = filter[i+r2][k];          //error
       filter[i+r2][k] = filter[i][k+c2];  //error
       filter[i][k+c2] = tmp2_4;         //error
    } 
   }
}

double **createmat(int rows,int cols){ 
  double **m; 
  m=new double*[rows];
   for(int i=0;i<rows;i++) 
      m[i]=new double[cols]; 
 
return m;
}

Code:

The strange thing is that it worked before inserting the typedef double**matriz;
I tested the function and it worked. Also, other function use this data and it works normally, example: (no errors at compiler time)

Code:

void pre_filter_Computations(matriz radius,matriz theta,int cols,int rows){ 

 double X[rows][cols],Y[rows][cols];
  double x[cols],y[rows];
 double epsilon = 0.0001;
 for(int i=0;i<cols;i++){ 
    x[i]=((double)(i-cols)/2)/((double)cols/2); 
 } 
 for(int z=0;z<rows;z++){ 
    y[z]=-(((double)(z-rows)/2)/((double)rows/2)); 
  } 
for(int m=0;m<cols;m++){ 
   for(int n=0;n<rows;n++){
      X[m][n]=x[m];
      Y[m][n]=y[n];
  }
 } 
     for(int a=0;a<rows;a++){ 
  for(int b=0;b<cols;b++){ 
    X[a][b] = pow(X[a][b],2);
    Y[a][b] = pow(Y[a][b],2); 
    X[a][b] = X[a][b] + Y[a][b]; 
    radius[a][b] = sqrt(X[a][b]); 
   }
       } 
     radius[rows/2][cols/2]=1;
      for(int a=0;a<rows;a++){
  for(int b=0;b<cols;b++){
    radius [a][b]= radius[a][b] + epsilon;
    theta[a][b] = atan2(Y[a][b],X[a][b])*180/PI; 
   } 
 }
}

Array subscripts must be of an integer type. Due to type promotions, when you add an integer and a double, the result type is double. This means that in for example

Code:

filter[i+r2][k+c2]

i+r2 and k+c2 produce a double value and this represents a constraint violation in the compiler. You can fix it by casting the result or the double operand to int

Code:

filter[i + (int)r2][k + (int)c2]

though the better approach is not to mix the types in the first place.