Operator weirdness with plus and minus-CodePudding

So, I was learning about the operators, and in particular, about binary operators.

In the following code:

int x=9;
x=-x;
cout<<x; // prints as -9

x= x;

cout<<x; //prints as -9

the question is why not as 9 or 9(contextual) than -9 ? why it works like this ?

CodePudding user response：

x=-x; means assign to x value which is negative to current x.

x= x; means assign to x value which is promoted to type int which is already an int. Since in this step x already has value -9 from previous operation nothing is changed and again -9 is printed.

Here are some docs.

CodePudding user response：

x=-x, or to make it more readable x = -x, is basically operation of reversing the sign of x.

x = x, is a trivial operation, since it copies x into x, since in previous operation the sign was reversed,x is -9, so now -9 is copied into x.

CodePudding user response：

int x=9;
x=-x; //What is this for ? you mean x = x - 1 ? In this case syntax should be  x -= x same for   expression.
cout<<x; // prints as -9
x= x;
cout<<x; //prints as -9

If above expressions are correct, but you're asking about -9 as end answer here is solution.

line 1: init x with 9.

line 2: assigned x with -(minus) of x which is -9

line 4: assigned x with (plus) of x which is (-9) equals -9

CodePudding user response：

Its a simple math problem. minus times a plus is a minus hence , a plus times a minus is still a minus. This is the easiest way to look at it.