I used the following code snippet:
bool plus = false;
int index = 0;
index = plus ? index++ : index--;
The index result is 0 and I do not know why, when I do the form below it works:
index += plus ? 1 : -1;
Does anyone have an explanation for this?
What does the post-increment operator do?
As already explained by @Jefferson Quesado . When you use for example index++ you are making a call to a function that will create an associated copy.
Explaining what happened in your code
Since you are a post increment operator, you first assign your variable index and then increment the copy.
What can you do?
index = plus ? index+1 : index-1;
Or, you can use the pre increment operator. This way you will be creating and changing the value of the associated copy, and then you will do the assignment.
index = plus ? ++index : --index;