def half1

bend-collections-laws-math@1.0.0.0 · proofs/math/random/proof_pcg.bend:85

import Base
import bend-collections-laws-math@1.0.0.0/spec/lib/common.bend as C
import bend-collections-laws-math@1.0.0.0/spec/math/w64.bend as SW
import bend-collections-laws-math@1.0.0.0/spec/math/random/pcg.bend as SP
import bend-collections-laws-math@1.0.0.0/src/math/u64.bend as WU
import bend-collections-laws-math@1.0.0.0/src/math/w64.bend as X
import bend-collections-laws-math@1.0.0.0/src/math/random/pcg.bend as P

85# the first half's value is t
86def half1(+cm: WU.U64, +hi: WU.U64, +t: Nat, +ht: {t == SP.dxsm1(SW.value(cm), SW.value(hi)) : Nat}) -> {SW.value(X.mul(P.xor64(hi, X.shr(hi, 32n)), cm)) == t : Nat}:
87  Equal.trans(Nat, SW.value(X.mul(P.xor64(hi, X.shr(hi, 32n)), cm)), SP.dxsm1(SW.value(cm), SW.value(hi)), t,
88    mulg(P.xor64(hi, X.shr(hi, 32n)), cm, SP.xor_bits(64n, SW.value(hi), C.high(32n, SW.value(hi))), xs32(hi), SW.value(cm), {==}),
89    Equal.sym(Nat, t, SP.dxsm1(SW.value(cm), SW.value(hi)), ht))