How Do Pointers to Arrays Differ Between C and Go, and What's the Preferred Approach in Go?

Using Pointers to Arrays in Go

In C, accessing an array through a pointer is a fundamental technique. However, in Go, there seems to be some ambiguity regarding this operation when dealing with slices. Let's delve into the details.

Consider the following C-style function that takes a pointer to an array:

void conv(int *x, int xlen, int *h, int hlen, int **y) {
    for (int i = 0; i < xlen; i++) {
        for (int j = 0; j < hlen; j++) {
            *(*y)[i + j] += x[i] * h[j];
        }
    }
}

In Go, however, attempting to access the pointer to the array, y, in a similar fashion results in a compiler error:

func conv(x []int, xlen int, h []int, hlen int, y *[]int) {
    for i := 0; i < xlen; i++ {
        for j := 0; j < hlen; j++ {
            *y[i+j] += x[i] * h[j]
        }
    }
}

The error message indicates that y[i j] is an index of type *[]int, which is invalid.

Passing Arrays and Slices

The solution to this problem lies in understanding the nature of arrays and slices in Go. According to the Go documentation, when passing an array to a function, it's usually better to pass a slice (a reference to the array) instead of a pointer to the array.

Using Slices Instead

To rewrite the conv function using slices, one can simply pass a slice of []int, as seen in the following example:

func conv(x []int, xlen int, h []int, hlen int, y []int) {
    for i := 0; i < xlen; i++ {
        for j := 0; j < hlen; j++ {
            y[i+j] += x[i] * h[j]
        }
    }
}

In this case, y is a regular slice, and accessing its elements is straightforward.

Conclusion

While the concept of using pointers to arrays is common in C, it's not typically recommended in Go. Instead, passing slices provides a more efficient and idiomatic way of referencing arrays in Go functions.

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