Similarly to the XOR method for integers, here is a clever way to swap any two numerical values without copy (the code is in C, but works the same for any language of course...):
double a = 157648.13;
double b = 96871.84;
printf("%.4f %.4f\n", a, b);
a = a + b;
b = a - b;
a = a - b;
printf("%.4f %.4f\n", a, b);
Just be careful with overflows, and enjoy ;)
