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Discuss: should we panic when powering 0 by 0? #303

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16 changes: 16 additions & 0 deletions ff/src/fields/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -178,6 +178,12 @@ pub trait Field:
/// least significant limb first.
#[must_use]
fn pow<S: AsRef<[u64]>>(&self, exp: S) -> Self {
// handle the special case when self = 0 and exp = 0
if self.is_zero() {
assert_ne!(exp.as_ref().iter().filter(|x| **x != 0u64).count(), 0);
return Self::zero();
}

let mut res = Self::one();

for i in BitIteratorBE::without_leading_zeros(exp) {
Expand Down Expand Up @@ -797,4 +803,14 @@ mod no_std_tests {
assert_eq!(expected, actual, "failed on test {:?}", i);
}
}

#[test]
#[should_panic]
fn pow_zero_by_zero() {
use crate::test_field::Fr;
use crate::Field;
use ark_std::Zero;

let _ = Fr::zero().pow(&[0u64, 0u64, 0u64, 0u64]);
}
}