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Make Int % Uint return a Uint#892

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andrewwhitehead wants to merge 1 commit intoRustCrypto:masterfrom
andrewwhitehead:fix/int-rem-uint
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Make Int % Uint return a Uint#892
andrewwhitehead wants to merge 1 commit intoRustCrypto:masterfrom
andrewwhitehead:fix/int-rem-uint

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@andrewwhitehead andrewwhitehead commented Jul 28, 2025

Fixes #847

The result of taking a signed integer modulo an unsigned one should be unsigned. Python agrees at least:

>>> hex(-0x112709385A4E59AFCE14364856CB6D1760D7D2B618A2DA9F85A96C4C2751D179 % 0xde157f812521c55eccf9a903b31e4a34)
'0x44bfe3176459710d0d0848f99b37e47b'
>>> hex(0x112709385A4E59AFCE14364856CB6D1760D7D2B618A2DA9F85A96C4C2751D179 % 0xde157f812521c55eccf9a903b31e4a34)
'0x99559c69c0c85451bff1600a17e665b9'

This also removes the RemAssign implementations, Int %= Uint. If somebody needs to do this, I think they can do a checked conversion to an Int for the modulus first.

@andrewwhitehead
make Int % Uint return a Uint
bdd8fc5 
Signed-off-by: Andrew Whitehead <cywolf@gmail.com>
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fjarri commented Jul 28, 2025 •
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I think in Rust's terms that makes it rem_euclid rather than rem.

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andrewwhitehead commented Jul 28, 2025

I think in Rust's terms that makes it rem_euclid rather than rem.

Yes, it's also possible to rename these methods to rem_euclid and add a separate RemEuclid trait. A checked_rem method that returned a CtOption<Int<LIMBS>> would also be possible (checking if the modulus fits in an Int).

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Bug in Int::div_rem_uint

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