# sub dd_str takes a string as its arg and returns
# the 2 doubles that form the doubledouble.
# Works correctly if default Math::MPFR precision is
# 2098 bits - else might return incorrect values.
sub dd_str {

  # Set $val to the 2098 bit representation of $_[0] 
  my $val = Math::MPFR->new($_[0]);

  # Most significant double is $val converted to a
  # double, rounding to nearest with ties to even
  my $msd = Rmpfr_get_d($val, MPFR_RNDN);

  $val -= $msd;

  # Least siginificant double is $val converted
  # to a double.
  return ($msd, Rmpfr_get_d($val, MPFR_RNDN));
}