Schnorr.check_r: def of bend-collections-laws-crypto@1.0.0.0
Import: import bend-collections-laws-crypto@1.0.0.0/spec/crypto/secp256k1/schnorr.bend as Schnorr
Lines 67-70 of bend-collections-laws-crypto@1.0.0.0/spec/crypto/secp256k1/schnorr.bend: https://jend.leeeet.dev/read.txt?path=bend-collections-laws-crypto@1.0.0.0/spec/crypto/secp256k1/schnorr.bend&start_line=67&end_line=70

import Base
import bend-collections-laws-crypto@1.0.0.0/spec/crypto/secp256k1/curve.bend as CV

# fail if is_infinite(R) or not has_even_y(R) or x(R) != r
def check_r(+r: Nat, inf: Bool, a: CV.SAffine) -> Bool:
  match a:
    case CV.SAffine{x, y}: Bool.and(Bool.not(inf), Bool.and(Nat.is_eq(Nat.mod(y, 2n), 0n), Nat.is_eq(x, r)))

Uses (7):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool.and
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool.not
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat.is_eq
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat.mod
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-crypto@1.0.0.0/spec/crypto/secp256k1/curve.bend&name=SAffine