sub double_to_bin {
   my $n = shift;

   my ( $s, $e, $m ) =
      unpack "a1 a11 a52",
         unpack "B64",
            pack "d>", $n;

   $e = oct( "0b$e" );
   if ( $e == 0x7FF ) {
      if ( $m =~ /^0+\z/ ) {
         return $s ? "-inf" : "+inf" ;
      } else {
         return "nan";
      }
   }

   my $n_bin = ( $e ? "1" : "" ) . $m;

   $e -= 1023;
   if ( $e < 0 ) {
      $n_bin = "0." . ( "0" x ( -$e - 1 ) ) . $n_bin;
   } else {
      my $z = ( $e + 1 ) - length( $n_bin );
      if ( $z >= 0 ) {
         $n_bin .= "0" x $z;
      } else {
         substr( $n_bin, $e+1, 0, "." );
      }
   }

   $n_bin =~ s/^0+(?=[01])//;
   if ( $n_bin =~ /\./ ) {
      #$n_bin =~ s/0+\z//;
      $n_bin =~ s/\.\z//;
   }

   $n_bin = ( $s ? "-" : "" ) . $n_bin;

   return $n_bin;
}