Can any one explain the output of this code?

Question

5.00/5 (1 vote)

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C++

int main ()
    {
        int x, y,z;
        x = 1;
        y = ++x * ++x;
        cout << "x="<<x <<" y= "<< y;
        z = ++x * ++x  * ++x;
        cout <<"\nx="<< x<<" z= " << z;
        return 0;
    }

Output:
x=3 y=9
x=6 z=150

Posted 20-Aug-15 20:51pm

the_beginner

Updated 20-Aug-15 21:09pm

CPallini

v2

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2 solutions

Solution 2

It is a matter of knowing C language funny functionalities, it is very complicated to come with an explanation easy to comprehend for newbies.

Better than an explanation, see it running !

Use the debugger and see what it does, step by step.

For this code, I recommend to run the debugger at assembly level in order to split lines of code to their components. Be very attentive to the variables while executing.

The whole program is about playing with the tricky ++

Posted 20-Aug-15 21:22pm

Patrice T

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CPallini · Accepted Answer · 2015-08-20T21:16:00

Solution 1

Such an example shows one of the weirdest corners of C/C++. I wouldn't even suggest a beginner to have a look at it. However, if you are interested you might find pretty complete info here: "Undefined behavior and sequence points" at Stack Overflow[^].

Posted 20-Aug-15 21:16pm

CPallini