cralgebra 0.2.1

A fast crypto algebra library
Documentation 
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use crate::*;

/// Exponentiation with optional runtime context.
///
/// This operation raises its first operand to the second
/// and return a value of the type of the former, optionally
/// taking an extra parameter that describes the
/// underlying algebraic structure at runtime.
///
/// The operation must not fail in any case.
///
/// The default implementation is usually reasonably performant.
pub trait PowDyn<
    C,
    D,
    Rhs: ClosedAddDyn<D> + ClosedSubDyn<D> + ZeroDyn<D> + OneDyn<D> + EuclidDyn<D>,
>: Sized + Clone + ClosedMulDyn<C> + OneDyn<C>
{
    /// Computes `self ^ rhs`. [Read more][PowDyn]
    fn pow_d(&self, rhs: &Rhs, ctx: &C, ctx2: &D) -> Self {
        if rhs.is_zero_d(ctx2) {
            return Self::one_d(ctx);
        }
        if rhs.is_one_d(ctx2) {
            // this check serves in case 1 + 1 == 0 under Rhs
            return self.clone();
        }
        let two = Rhs::one_d(ctx2).add_d(&Rhs::one_d(ctx2), ctx2);
        let (q, r) = rhs.euclid_div_rem_d(&two, ctx2);
        let mut x = self.pow_d(&q, ctx, ctx2);
        x = x.mul_d(&x, ctx);
        if r.is_one_d(ctx2) {
            x.mul_assign_d(self, ctx);
        }
        x
    }
}