Passing a pointer representing a 2D array to a function in C++

by

Regarding the edit: to pass this double stuff[3][3] to a C function, you could

1) pass a pointer to the whole 2D array:

void dostuff(double (*a)[3][3])
{
// access them as (*a)[0][0] .. (*a)[2][2]
}
int main()
{
    double stuff[3][3];
    double (*p_stuff)[3][3] = &stuff;
    dostuff(p_stuff);
}

2) pass a pointer to the first 1D array (first row) and the number of rows

void dostuff(double a[][3], int rows)
{
// access them as a[0][0] .. a[2][2]
}
int main()
{
    double stuff[3][3];
    double (*p_stuff)[3] = stuff;
    dostuff(p_stuff, 3);
}

3) pass a pointer to the first value in the first row and the number of both columns and rows

void dostuff(double a[], int rows, int cols)
{
// access them as a[0] .. a[8];
}
int main()
{
    double stuff[3][3];
    double *p_stuff = stuff[0];
    dostuff(p_stuff, 3, 3);
}

(that this last option is not strictly standards-compliant since it advances a pointer to an element of a 1D array (the first row) past the end of that array)

If that wasn’t a C function, there’d be a few more options!

More Related Contents:

  1. Invalid operands to binary expression while implementing vector [closed]
  2. For loop with an array
  3. Difficulties on atributting a array to another [closed]
  4. can’t extract data from a structure array c++ [closed]
  5. How would I implement Arrays into this code
  6. Dynamic memory allocation of array in C & C++
  7. Assigning char array from ifstream breaks array if adding another char to array
  8. The array index doesnt show the character [closed]
  9. How do I declare a 2d array in C++ using new?
  10. What happens if I define a 0-size array in C/C++?
  11. Initialization of all elements of an array to one default value in C++?
  12. How to return an array from a function?
  13. Can placement new for arrays be used in a portable way?
  14. When passing an array to a function in C++, why won’t sizeof() work the same as in the main function?
  15. Printing an array in C++?
  16. Comparing arrays for equality in C++
  17. c++ array assignment of multiple values
  18. What is the simplest way to convert array to vector?
  19. Common array length macro for C? [duplicate]
  20. How do you initialise a dynamic array in C++?
  21. pointer to array c++
  22. Finding smallest value in an array most efficiently
  23. Can std::begin work with array parameters and if so, how?
  24. How can I make `new[]` default-initialize the array of primitive types?
  25. What is the use of 0-length array (or std::array)?
  26. can’t modify char* – Memory access violation
  27. Braces around string literal in char array declaration valid? (e.g. char s[] = {“Hello World”})
  28. how do arrays work internally in c/c++
  29. How to convert a byte array into double in C?
  30. How can a char pointer be initialized with a string (Array of characters) but an int pointer not with an array of integer? [duplicate]

Leave a Comment