4 ms·

Author also wrote "Learn Rust the dangerous way". > In this series, I'm trying something different. Let's take a grungy, optimized, pointer-type-punning, SSE-u

• rvr_ 7y ago
  I dislike nitpicking, but the following is wrong: "In C, bodies[i] is exactly the same as *(bodies + i) — it performs pointer arithmetic and a dereference and nothing else. In particular, it assumes that you have some reason to know that i is a valid index for the array. This is the common case in C and gets a shorthand using square brackets." In C, bodies[i] is not (bodies + i), with the exception being char arrays. The general rule is: bodies[i] = *(bodies + i * sizeof(bodies[0]))
  • heinrich5991 7y ago
    No, it's actually defined to be the same. The pointer arithmetic in C follows your intuitive understanding of array indexing. #include <stdio.h> int main() { int array[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16}; printf("%d %d\n", array[4], *(array + 4)); return 0; } prints "4 4".
  • barrkel 7y ago
    + in C advances pointers in sizeof-pointed-to thing increments. It's why ++ works too. Similarly - on pointers returns a difference in units of sizeof-pointed-to thing.
  • jcranmer 7y ago
    The semantics of a[i] is exactly that of *(a + i). Which is why i[bodies] is actually legal C code.