Statements in a function -calculations

[fcisconj]

i am studying the basics, i'm at Functions II

The following is given here. ( my question is after.)

#include <iostream>
using namespace std;

void duplicate (int& a, int& b, int& c)
{
  a*=2;
  b*=2;
  c*=2;
}

int main ()
{
  int x=1, y=3, z=7;
  duplicate (x, y, z);
  cout << "x=" << x << ", y=" << y << ", z=" << z;
  return 0;
}

the output is

x=2, y=6, z=14



but how did the following double the numbers?
{
a*=2;
b*=2;
c*=2;
}


was that some type of math i missed in H.S?
hopefully it was a lesson of c++ i missed.

by the way i understand the entire lesson accept for that one peice.

here is where the totorial is located:
http://www.cplusplus.com/doc/tutorial/functions2.html

any help is much appreciated.

[kashmoney2006]

a*=x
is the same as
a = a * x

so a*=2 is the same as a = a *2.

so it takes the original value of a, multiplies is by two, and sticks it back into the value of a.

hope this helps.

[vince1027]

It's generally a C (not C++) syntax of "operate and assign back" (as I call it) operator.

a += 2;
b -= 2;
c *= 2;
d /= 2;

are equivalently the same as

a = a + 2;
b = b - 2;
c = c * 2;
d = d / 2;

But you need to note that operators in C++ can be overloaded. The equivalences I mentioned above is applicable for primitive data types. If the variables are objects it may or may not mean the same thing.

[fcisconj]

GOT IT. Easy to remember.

Thank you all very much.