A member of an rvalue expression is an rvalue. The standard states in 5.3.5 [expr.ref]: If E2 is declared to have type “reference to T”, then E1.E2 is an lvalue […] – If E2 is a non-static data member, and the type of E1 is “cq1 vq1 X”, and the type of E2 is “cq2 … Read more
C doesn’t have references. In C++ ++i returns a reference to i (lvalue) whereas in C it returns a copy(incremented). C99 6.5.3.1/2 The value of the operand of the prefix ++ operator is incremented. The result is the new value of the operand after incrementation. The expression ++Eis equivalent to (E+=1). ‘‘value of an expression’’ … Read more
string literals are lvalues, but you can’t change them rvalue, but if it’s a pointer and non-NULL, the object it points to is an lvalue The C standard recognizes the original terms stood for left and right as in L = R; however, it says to think of lvalue as locator value, which roughly means … Read more
Use -insertObject:atIndex: or replaceObjectAtIndex:withObject:.
The standard correctly defines the return type of an assignment operator. Actually, the assignment operation itself doesn’t depend on the return value – that’s why the return type isn’t straightforward to understanding. The return type is important for chaining operations. Consider the following construction: a = b = c;. This should be equal to a … Read more
Is bar an rvalue or an lvalue? The question answers itself. Whatever has a name is an lvalue(1). So bar is an lvalue. Its type is “rvalue reference to string“, but it’s an lvalue of that type. If you want to treat it as an rvalue, you need to apply std::move() to it. If you … Read more
No, the return value of a function is an l-value if and only if it is a reference (C++03). (5.2.2 [expr.call] / 10) If the type returned were a basic type then this would be a compile error. (5.17 [expr.ass] / 1) The reason that this works is that you are allowed to call member … Read more
Expressions don’t have return types, they have a type and – as it’s known in the latest C++ standard – a value category. A conditional expression can be an lvalue or an rvalue. This is its value category. (This is somewhat of a simplification, in C++11 we have lvalues, xvalues and prvalues.) In very broad … Read more
Yes, *this is always an lvalue, no matter how a member function is called, so if you want the compiler to treat it as an rvalue, you need to use std::move or equivalent. It has to be, considering this class: struct A { void gun() &; // leaves object usable void gun() &&; // makes … Read more
The standard correctly defines the return type of an assignment operator. Actually, the assignment operation itself doesn’t depend on the return value – that’s why the return type isn’t straightforward to understanding. The return type is important for chaining operations. Consider the following construction: a = b = c;. This should be equal to a … Read more