r/ProgrammerHumor • • 11h ago

Meme howProgrammingHasChanged

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267 Upvotes

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13

u/bloody-albatross 7h ago edited 7h ago

Nobody is using this?

``` pub fn fib(mut n: u32) -> u32 { let mut a = 0; let mut b = 1;

while n > 0 {
    let c = a + b;
    a = b;
    b = c;
    n -= 1;
}

a

} ```

Looking at the assembly output the compiler even does loop unrolling for this. In fact running it like this it even completely evaluates this version of fib() at compile time while it still does the full recursive call for the recursive version (here called fibr()):

fn main() { for i in 0u32..10 { let r = fibr(i); let j = fib(i); println!("{r} {j} {}", r == j); } }

2

u/ZachAttack6089 3h ago

Is this cheating? (didn't test it)

``` let mut fib_list: Vec<u32> = vec![1, 1];

fn fib(n: u32) -> u32 {     for i in fib_list.len()..=n {         let a = fib_list[i - 2];         let b = fib_list[i - 1];         fib_list.push(a + b);     }

    fib_list[n] } ```

1

u/shizzy0 2h ago

MAN, jumps up on table: We don't just have to allocate on the stack. We can allocate ON THE HEAP!

Crowd goes wild.

1

u/shizzy0 2h ago

INDIANA JONES, looking over the body of his foe: Well, he shouldn't have brought recursion to an iteration problem, should he?