This is how I posted a method from C to Swift. I tested it well, it seems to work. It's there a way to write this better, following good practices of Swift? The original is in C and the target must be in Swift.

Original C Code:

inline float mac(const float *a, const float *b, unsigned int size)
    float sum = 0;
    unsigned int i;

    for (i = 0; i < size; i++)
        sum += (*a++) * (*b++);
    return sum;

and the translation to Swift:

func mac(a : [Float], b : [Float], size : Int) -> Float
    var sum : Float = 0;

    for (var i = 0; i < size; i++){
        sum += (a[i]) * (b[i]);
return sum;

1 Answer 1


You can remove the size parameter as arrays know their own size in Swift, and use the zip, map and reduce functions to perform the computation rather than the C-style for loop, which is now unavailable in the latest versions of Swift (as is i++):

func mac(a: [Float], b: [Float]) -> Float {
    return zip(a, b).map(*).reduce(0, +)
  • The zip function takes two arrays and makes a single array of tuples, with each tuple containing the nth element from each array.
  • The map function changes each element of the array with a user-supplied function. In this case, the multiplication operator is passed in, which multiplies each pair.
  • The reduce function performs the task of summing each result (starting at 0).
  • \$\begingroup\$ But just for my knowledge, was my implementation correct from the functionality point of view? \$\endgroup\$
    – Duarte
    Feb 8, 2016 at 17:50
  • 1
    \$\begingroup\$ Yes, it looked correct, but can be considered "old fashioned" for use in Swift. \$\endgroup\$
    – Robert
    Feb 8, 2016 at 17:51
  • 1
    \$\begingroup\$ Also, C-style for loops won't work in future versions of Swift. \$\endgroup\$ Feb 13, 2016 at 18:57

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