What does * in front of = mean?

Question

Hello everyone I have a very simple question that I just don't understand. I've tried googling it but haven't found a clear answer.

What is x after the following statements?

int x = 2;
int y = 1;
x *= y + 1;

I know that the answer is 4 but I don't understand why it is 4. Just need some clarity on what x* means exactly. Thanks!

If you know what `x += y` means, then `x -= y`, `x *= y`, `x /= y`, and `x %= y` should all be intuitive. See [Compound assignment operators in Java](https://www.geeksforgeeks.org/compound-assignment-operators-java/) — Andreas, Dec 01 '18 at 00:32

score 2 · Answer 1 · answered Nov 30 '18 at 23:31

2

I think this line is the one why you ask

x *= y + 1;

This is a shorthand for

x = x * (y + 1);

This works also with other operators like - and +, when the first variable is the same as the variable on the left side (which will be assigned).

answered Nov 30 '18 at 23:31

Donat

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Andrei Dumitrescu-Tudor · Answer 2 · 2018-11-30T23:54:31.253

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The x*= symbol means x=x* the result of whatever you put after the equals symbol.

x*= y+1 will turn to x = x * (y+1). The expresion you put after equals is evaluated first and then multiplied with x. The result will be cast to the type of the assignment variable (x).

edited Nov 30 '18 at 23:54

answered Nov 30 '18 at 23:29

Andrei Dumitrescu-Tudor

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Actually, it doesn't mean that. 1) there is a typecast, 2) you are ignoring operator precedence. In fact, `x *= ;` really means `x = ()(x * ());`. And yes, there are situations where the typecast and/or precedence **will** matter. – Stephen C Nov 30 '18 at 23:48
@StephenC updated my answer. – Andrei Dumitrescu-Tudor Nov 30 '18 at 23:54

score 0 · Answer 3 · answered Nov 30 '18 at 23:31

0

Of course x is 4, if you don't understand the last statement, you can read it like this

x = x * y + 2

answered Nov 30 '18 at 23:31

chinloyal

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What does * in front of = mean?

3 Answers3