Minor issues about Heliocentric.cpp about cpbook-code HOT 4 CLOSED

On an unrelated note, this is my preferred way of implementing Extended Euclidean algorithm (which is shorter and clearer but may be slightly slower).

void extEuclid(int& d, int& x, int& y, int a, int b) {
  if (a == 0) {
    d = b; x = 0; y = 1;
    return;
  }
  extEuclid(d, y, x, b % a, a);
  x -= b / a * y;
}

from cpbook-code.

from cpbook-code.

for better readability, the code can be written as follows.
tie(a, b) = tuple(b, a%b);
tie(x, xx) = tuple(xx, x-qxx);
tie(y, yy) = tuple(yy, y-qyy);

Accepted, this is Pythonic way, and I am using C++17 anyway so ok

this is my preferred way of implementing Extended Euclidean algorithm

better not, we prefer iterative?

is not needed in most places since in most intermediate steps it doesn't hurt to have negative values
leave it :), it makes the explanation simpler, no need to chase for constant factor speed

from cpbook-code.

Ok, I'll change the multiple assignment code and leave the other two unchanged.

from cpbook-code.