Bigint.Mag.modpow: def of bend-kit-bignum@0.1.0.0
Import: import bend-kit-bignum@0.1.0.0/bigint.bend as Bigint
Lines 274-286 of bend-kit-bignum@0.1.0.0/bigint.bend: https://jend.leeeet.dev/read.txt?path=bend-kit-bignum@0.1.0.0/bigint.bend&start_line=274&end_line=286

import Base

# b^e * acc mod m, with b and acc below m. f counts e's bits: 14 per limb,
# since 10^4 < 2^14.
def Mag.modpow(+f: Nat, +b: List<&2, U32>, +e: List<&2, U32>,
  +acc: List<&2, U32>, +m: List<&2, U32>) -> List<&2, U32>:
  match f:
    case 0n:
      acc
    case 1n+g:
      +h = Mag.half(e)
      +acc2 = Mag.if(List<&2, U32>, Mag.odd(e),
        u => Mag.rem(Mag.mul(acc, b), m), u => acc)
      Mag.if(List<&2, U32>, List.is_empty(&2, U32, h), u => acc2,
        u => Mag.modpow(g, Mag.rem(Mag.mul(b, b), m), h, acc2, m))

Uses (9):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List.is_empty
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32
  https://jend.leeeet.dev/definition.txt?path=bend-kit-bignum@0.1.0.0/bigint.bend&name=Mag.half
  https://jend.leeeet.dev/definition.txt?path=bend-kit-bignum@0.1.0.0/bigint.bend&name=Mag.if
  https://jend.leeeet.dev/definition.txt?path=bend-kit-bignum@0.1.0.0/bigint.bend&name=Mag.mul
  https://jend.leeeet.dev/definition.txt?path=bend-kit-bignum@0.1.0.0/bigint.bend&name=Mag.odd
  https://jend.leeeet.dev/definition.txt?path=bend-kit-bignum@0.1.0.0/bigint.bend&name=Mag.rem