Add TryInto<u512, u256>

[delaaxe]

This change is 

[orizi]

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

a discussion (no related file):
any particular usecase for this?
in general we only use u512 for modular operation back into u256.

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[delaaxe]

Our use case is using the first return value of u512_safe_div_rem_by_u256 as a u256

[orizi]

Reviewed 2 of 2 files at r1, all commit messages.
Reviewable status: all files reviewed, 3 unresolved discussions (waiting on @delaaxe)

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corelib/src/integer.cairo line 1384 at r2 (raw file):

        }
    }
}

no need (it was required in some specific other instances)

Suggestion:

impl U512TryIntoU256 of TryInto<u512, u256> {
    fn try_into(self: u512) -> Option<u256> {
        if self.limb2 != 0 || self.limb3 != 0 {
            Option::None
        } else {
            Option::Some(u256 { low: self.limb0, high: self.limb1 })
        }
    }
}

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corelib/src/test/integer_test.cairo line 811 at r2 (raw file):

    };
    let option: Option<u256> = num.try_into();
    assert(option.is_none(), 'u512 -/-> u256');

Suggestion:

    assert!(u512 { limb0: 1, limb1: 2, limb2: 0, limb3: 0 }.try_into() == Option::Some(0x200000000000000000000000000000001_u256));
    assert!(u512 { limb0: 1, limb1: 2, limb2: 3, limb3: 0 }.try_into() == Option::<u256>::None);
    assert!(u512 { limb0: 1, limb1: 2, limb2: 0, limb3: 4 }.try_into() == Option::<u256>::None);
    assert!(u512 { limb0: 1, limb1: 2, limb2: 3, limb3: 4 }.try_into() == Option::<u256>::None);

[delaaxe]

Reviewable status: 0 of 10 files reviewed, 2 unresolved discussions (waiting on @orizi)

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corelib/src/integer.cairo line 1384 at r2 (raw file):

Previously, orizi wrote…

no need (it was required in some specific other instances)

Done.

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corelib/src/test/integer_test.cairo line 811 at r2 (raw file):

    };
    let option: Option<u256> = num.try_into();
    assert(option.is_none(), 'u512 -/-> u256');

Done.

[orizi]

Reviewed 1 of 2 files at r4, 8 of 8 files at r5, 1 of 1 files at r6, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @delaaxe)

a discussion (no related file):
@gilbens-starkware for 2nd eye.

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[orizi]

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @delaaxe)

[gilbens-starkware]

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @delaaxe)

[orizi]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @delaaxe)