What is the reason for the value of a = -1 in the final step?

#1

int main()
{
int a = INT_MAX;
a=a<<1;
cout<<a<<endl;
cout<<++a<<endl;
a=a++;
cout <<a<<endl;
return 0;
}

Now the output it is showing is :
2147483647
-2
-1
-1
the last value should be 0 according to me. why is it -1?

#2

why last one should be 0??

#3

the final output is -1 . I wanted to know why it should be -1 and not 0.

#4

Hey @abhaysota
The assignment operator ( = ) has lower precedence than any primary operator, such as ++x or x++ . That means that in the line

a=-1;

a = a++;

the right hand side is evaluated first. The expression a++ increments a to 0, then returns the original value -1 as a result, which is used for the assignment.

In other words, your code is equivalent to

// Evaluate the right hand side:
int incrementResult = a;   // Store the original value, int incrementResult = -1
a = a + 1;                 // Increment a, i.e. a = 0

// Perform the assignment:
a = incrementResult;       // Assign c to the "result of the operation", i.e. a = -1

Compare this to the prefix form

a = ++a;

which would evaluate as

// Evaluate the right hand side:
a = a + 1;                 // Increment a, i.e. a = 0
int incrementResult = a;   // Store the new value, i.e. int incrementResult = 0

// Perform the assignment:
a = incrementResult;       // Assign c to the "result of the operation", i.e. a=0