- we actually measure the number of memory allocations
      performed rather than the number of temporaries directly, note also that the
      <a href="http://gmplib.org/manual/C_002b_002b-Interface-Floats.html#C_002b_002b-Interface-Floats" target="_top">mpf_class</a>
      wrapper that will be supplied with GMP-5.1 reduces the number of temporaries
      to pretty much zero). Note that if we compile with expression templates disabled
      and rvalue-reference support on, then actually still have no waste