def mask_pair
bend-collections-laws-crypto@1.0.0.0 · proofs/math/random/uint64n.bend:249
import bend-collections-laws-crypto@1.0.0.0/proofs/math/random/uint64n.bend as Uint64n
import Base
import bend-collections-laws-crypto@1.0.0.0/spec/math/w64.bend as SW
import bend-collections-laws-crypto@1.0.0.0/spec/math/random/rand.bend as SR
import bend-collections-laws-crypto@1.0.0.0/spec/math/random/source.bend as SRC
import bend-collections-laws-crypto@1.0.0.0/src/math/u64.bend as WU
import bend-collections-laws-crypto@1.0.0.0/src/math/w64.bend as X
import bend-collections-laws-crypto@1.0.0.0/src/math/random/rand.bend as R
import bend-collections-laws-crypto@1.0.0.0/spec/math/random.bend as SRM
249def mask_pair(-S: Data, +n: WU.U64, +m: Nat, p: WU.U64 & S, +hv: {SW.value(n) == 1n+m : Nat}) -> {SRM.val_pair(S, R.mask(S, n, p)) == (SR.and_bits(64n, SW.value(SRC.fst64(S, p)), m), SRC.snd64(S, p)) : Nat & S}:
250 match p:
251 case Tuple{+x, +s1}:
252 Equal.cong(Nat, Nat & S, z => (z, s1), SW.value(R.and64(x, X.sub(n, one64()))), SR.and_bits(64n, SW.value(x), m), mask_value(x, n, m, hv))