Pre-increment and Post-increment in C/C++
Pre-increment operator: A pre-increment operator is used to increment the value of a variable before using it in a expression. In the Pre-Increment, value is first incremented and then used inside the expression.
a = ++x;
Here, if the value of ‘x’ is 10 then value of ‘a’ will be 11 because the value of ‘x’ gets modified before using it in the expression.
Pre Increment Operation a = 11 x = 11
Post-increment operator: A post-increment operator is used to increment the value of variable after executing expression completely in which post increment is used. In the Post-Increment, value is first used in a expression and then incremented.
a = x++;
Here, suppose the value of ‘x’ is 10 then value of variable ‘b’ will be 10 because old value of ‘x’ is used.
Post Increment Operation a = 10 x = 11
Special Case for Post-increment operator: If we assign the post-incremented value to the same variable then the value of that variable will not get incremented i.e. it will remain the same like it was before.
a = a++;
Here, if the value of ‘x’ is 10 then value of ‘a’ will be 10 because the value of ‘x’ gets assigned to the post-incremented value of ‘x’.
Value of x before post-incrementing x = 10 Value of x after post-incrementing x = 10
This special case is only with post-increment and post-decrement operators, while the pre-increment and pre-decrement operators works normal in this case.
Evaluating post and pre-increment together
Precedence of postfix ++ is more than prefix ++ and their associativity is also different. Associativity of prefix ++ is right to left and associativity of postfix ++ is left to right.
- Associativity of postfix ++ is left to right
- Associativity of prefix ++ is right to left
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