help with looping structure

[laserlight]

Are you sure that it is C/C++ standard?

Yes. Besides, if it was not, the result of an expression such as (9 - 5 - 2) would be implementation defined.

I lastly debugged code with overloaded operator+ and I mean to have seen that a+b+c was evaluated as a+(b+c).

That is strange. Perhaps for the sake of optimisation for operator+ this grouping rule might be violated, but that seems rather unlikely where an overloaded operator+ is concerned.