feat(corelib): OptionTrait::get_or_insert_with

[hudem1]

Inserts a value computed from a provided closure into the option if it is [None], then returns the contained value.

Example

let mut x = Option::None;
let y = x.get_or_insert_with(|| 5);
assert_eq!(y, 5);

let mut x = Option::Some(2);
let y = x.get_or_insert_with(|| 5);
assert_eq!(y, 2);

[reviewable-StarkWare]

This change is 

[orizi]

Reviewed all commit messages.
Reviewable status: 0 of 2 files reviewed, 1 unresolved discussion (waiting on @hudem1)

---

corelib/src/option.cairo line 812 at r1 (raw file):

        };

        self.unwrap()

Suggestion:

        match self {
            Option::Some(value) => value,
            Option::None => {
                let value = f();
                self = Option::Some(value);
                value    
            }
        }

[orizi]

i'm not sure we should have this, as it makes much more sense if there's mutability in the language, which there isn't.

Reviewable status: 0 of 2 files reviewed, 1 unresolved discussion (waiting on @hudem1)

[hudem1]

Yes, I see what you mean! What should we do then ? The function take is in the same case too then.

Reviewable status: 0 of 2 files reviewed, 1 unresolved discussion (waiting on @orizi)

---

corelib/src/option.cairo line 812 at r1 (raw file):

        };

        self.unwrap()

Done.

[orizi]

no - the take is actually ok - as its return value isn't a reference in rust as well.

Reviewed all commit messages.
Reviewable status: 0 of 2 files reviewed, 1 unresolved discussion

[hudem1]

Ok yes okay! Makes sense!

Let me know once you've decided whether we want to include this method. In my opinion, the method still fulfills its core purpose - retrieving a value if it exists, or inserting one if it doesn't - so, it can still be useful. But I understand it won't be as versatile as in Rust where we can get a mutable reference to the value inside.

Reviewable status: 0 of 2 files reviewed, 1 unresolved discussion (waiting on @orizi)

[orizi]

i think it shouldn't - because:

1. the current version is too easily replaced with:

let x = opt.unwrap_or_else(f);
opt = Some(x);
x

2. If we do have some sort of mutability added - this would block the function from providing it.

Reviewable status: 0 of 2 files reviewed, 1 unresolved discussion

[hudem1]

yeah ok I understand! I will close the PR then!

Reviewable status: 0 of 2 files reviewed, 1 unresolved discussion (waiting on @orizi)