(use numbers)

#>
               void double_to_uint64(double d, ___out uint32_t& hi, ___out uint32_t& li)
               {
                 union { double d; uint64_t i; } mem;
                 mem.d = d;
                 li = mem.i;
                 hi = mem.i >> 32;
               }
<#

(define double->uint64 (foreign-lambda void "double_to_uint64" double (ref unsigned-integer32) (ref unsigned-integer32)))

(let ((hi 0)
      (li 0))
  (double->uint64 1.3 hi li)