Ecdsa.recover_r: def of bend-collections-laws-crypto@1.0.0.0
Import: import bend-collections-laws-crypto@1.0.0.0/src/crypto/secp256k1/ecdsa.bend as Ecdsa
Lines 224-232 of bend-collections-laws-crypto@1.0.0.0/src/crypto/secp256k1/ecdsa.bend: https://jend.leeeet.dev/read.txt?path=bend-collections-laws-crypto@1.0.0.0/src/crypto/secp256k1/ecdsa.bend&start_line=224&end_line=232

import Base
import bend-collections-laws-crypto@1.0.0.0/src/crypto/secp256k1/scalar.bend as S
import bend-collections-laws-crypto@1.0.0.0/src/crypto/secp256k1/point.bend as P

# Q = r^-1 (s R - z G), with R the point of x-coordinate r + n j (j = id / 2)
# and y parity id mod 2
def recover_r(+z: List<&2, Nat>, +r: List<&2, Nat>, +s: List<&2, Nat>, m: Maybe<&2, P.Point>) -> Maybe<&2, List<&2, U32>>:
  match m:
    case None{}: None{}
    case Some{+pr}:
      +ri = S.inv(r)
      +q = P.add(P.mul(S.mul(S.neg(z), ri), P.g()), P.mul(S.mul(s, ri), pr))
      recover_q(q, P.is_inf(q))

Uses (13):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Maybe
  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-collections-laws-crypto@1.0.0.0/src/crypto/secp256k1/ecdsa.bend&name=recover_q
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-crypto@1.0.0.0/src/crypto/secp256k1/point.bend&name=Point
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-crypto@1.0.0.0/src/crypto/secp256k1/point.bend&name=add
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-crypto@1.0.0.0/src/crypto/secp256k1/point.bend&name=g
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-crypto@1.0.0.0/src/crypto/secp256k1/point.bend&name=is_inf
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-crypto@1.0.0.0/src/crypto/secp256k1/point.bend&name=mul
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-crypto@1.0.0.0/src/crypto/secp256k1/scalar.bend&name=inv
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-crypto@1.0.0.0/src/crypto/secp256k1/scalar.bend&name=mul
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-crypto@1.0.0.0/src/crypto/secp256k1/scalar.bend&name=neg