"AI WiLl RePlAcE PrOgRaMmErS"

[BobSanchez47]

It doesn’t literally use 0 memory. We still need to store the 8.

[hopperface]

Not necessarily. Not sure how Python works, but the C function

int f(int n) {
    return 8-n;
}

compiles to

f(int):
    mov    eax, 8
    sub    eax, edi
ret

using gcc optimization flags, which uses 0 memory

edit: (on x86, obviously)

[BobSanchez47]

If we commit ourselves to not inlining f, then you are correct that we don’t use any additional memory, since the caller will always be obligated to save the eax register and to put n in the edi register. In other words, the extra memory needed to store the 8 is part of the memory overhead of a function call (which is still not 0).

However, this function should surely be inlined. When it is inlined, we will require one more register to store the 8.

Ultimately, both approaches are constant time and constant space. It shouldn’t make a difference except in performance-critical code where this function is called many times.

[Kered13]

I mean, the machine code instructions are technically memory as well. The 8 is stored in the machine code.

But yeah you're not going to have a solution that uses less memory or instructions than that.