1. cout << string_1 << string_2 << string_3;

The line above is processed from left to right, first the operator "<<" operates on "cout" and "string_1", which returns an ostream object which is later used to operate on "string_2", and so on to "string_3".

2. a = b = 5;

In the line above, the code is processed from right to left. First the operator "=" operates on "b" and "5", which returns an int object to operate with "a" on the next "=" operator.

I might be wrong on how these lines are processed.

Please help me understand why the compiler is changing the order of operations in both cases.

CodePudding user response：

Because that's how the operator associativity is defined: https://en.cppreference.com/w/cpp/language/operator_precedence

– UnholySheep

CodePudding user response：

This is a wise design decision.

Because you intuitively expect

cout<< string_1 << string_2 << string_3;

to emit the three strings in that order, and you expect

a = b = 5;

to assign 5 to both a and b (rather than performing a= b; b= 5;)