c = a +++ b运算是什么意思？

Question

The following code has me confused

int a=2,b=5,c;
c=a+++b;
printf("%d,%d,%d",a,b,c);

I expected the output to be 3,5,8, mainly because a++ means 2 +1 which equals 3, and 3 + 5 equals 8, so I expected 3,5,8. It turns out that the result is 3,5,7. Can someone explain why this is the case?

Answer 1

It's parsed as c = a++ + b , and a++ means post-increment, ie increment after taking the value of a to compute a + b == 2 + 5 .

Please, never write code like this.

Answer 2

Maximal Munch Rule applies to such expression, according to which, the expression is parsed as:

c = a++ + b;

That is, a is post-incremented ( a++ ) and so the current value of a (before post-increment) is taken for + operation with b .

Answer 3

a++ is post incrementing, ie the expression takes the value of a and then adds 1.
c = ++a + b would do what you expect.

Answer 4

This is an example of bad programming style.

It is quite unreadable, however it post increments a so it sums the current value of a to b and afterwards increments a !

Answer 5

a++ gets evaluated after the expression.

c = ++a + b; would give you what you thought.

Answer 6

The post increment operator, a++, changes tge value of a after the value of a is evaluated in the expression. Since the original value of a is 2, that's what's used to compute c; the value of a is changed to reflect the new value after the ++ is evaluated.

Answer 7

a ++ + b ..it给出结果7，由于后置增量运算符，a的表达式值更新为3之后

Answer 8

According to Longest Match rule it is parsed as a++ + +b during lexical analysis phase of compiler. Hence the resultant output.

Answer 9

Here c= a+++b; means c= (a++) +b; ie post increment. In a++, changes will occur in the next step in which it is printing a, b and c. In ++a, ie prefix-increment the changes will occur in the same step and it will give an output of 8.