# hi, any JS or BigNum-math expert around ? I have a mix-function from RapidHash
# in TS/JS :
function rapid_mix_fast(a: bigint, b: bigint): bigint {
  const m = a  b;
  return BigInt.asUintN(64, m) ^ (m >> 64n);
}```
and in Nim :
# nim# proc mixFast( a,b :uint64 ) :uint64 =
#   let
#     hiBits :uint64 = 0'u64
#     m      = mulx_u64(a,b, hiBits.addr)
#     loBits = a  b
#   debugEcho " hiBits-", hiBits, "  m-",m , ", loBits-",loBits
#   result = (m xor hiBits)

# echo mixFast( 34'u64, 1647675675699997562'u64)
For given `a` and `b`the lower 64-bits `loBits` are not the same ? The intrinsic
`mulx_u64` writes the upper 64-bits to `hiBits` - which gives `3`on JS ann Nim.
The lower part have a diff of `4145` ?