In case of evaluation of postfix expression , is the associativity always left to right?. If yes, why? If no, why?
Yes.
See this handy table of C's operators.
The postfix operators are:
++and--()(function call)[](array indexing).(member select)->(member select)
And they are all in the left-to-right precedence group (2) near the top of the table.
I guess the "why" is since that's how the language is defined. There are no "natural causes" for these kinds of things, they're human-made you know.
来源：https://stackoverflow.com/questions/21407061/is-left-associativity-only-for-postfix-expression