Value of b for a=5 in following b=a++*++a

Question

Tell me the value of a and b of incriment topic in c program

Answer 1

If you can yry with different compilers, you should get warnings and different results.

Answer 2

Edit: I was wrong. See answers below for explanation.

This particular issue concerns operator precedence.
"Operator precedence determines the grouping of terms in an expression. This affects how an expression is evaluated. Certain operators have higher precedence than others;"

https://en.cppreference.com/w/c/language/operator_precedence

So, i believe the value of b=35 (in c11)

Answer 3

Mateusz Kempa
Can you describe how that number comes as output? (I know the output as I have test ran the code). But how the expression is parsed and which part of the expression gets higher priority to be processed?

Answer 4

Actually, my answer was not enterily correct. AndreaC is right. Multiple unsequenced modifications is undefined behavior.

Logic i was following (so was my compiler):
The ++ operator has a result and a side effect. In the expression b = a++, the result of a++ is the current value of a - that's what gets assigned to b. The side effect of a++ is to add 1 to
prefix++ operator evaluates to the incremented value of its operand //hence b=5*7=35

However, in this case order of evaluation can be different and depends on your programming enviroment
Conclusion: do not risk unspecified behavior. It is recommended to avoid this kind of confusing expressions.

//Side conclusion: bloody C... you never stop learning it ;)

Answer 5

Thanks for clarification Mateusz Kempa 👍

Answer 6

Oh ok you were actually saying that it depends on compiler uesd