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In C++, pre-increment operator gives lvalue because incremented object itself is returned, not a copy. But in C, it gives rvalue. Why?
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1) Pre-increment operator: A pre-increment operator is used to increment the value of a variable before using it in an expression. In the Pre-Increment, value is first incremented and then used inside the expression.
If the counter is a fundamental type and the result of increment is not used, then it makes no difference whether you use post/pre increment. If the counter is not a fundamental type and the result of the increment is not used and optimizations are disabled, then pre increment may be more efficient.
The pre increment operator is used to increment the value of some variable before using it in an expression. In the pre increment the value is incremented at first, then used inside the expression. if the expression is a = ++b; and b is holding 5 at first, then a will hold 6.
An lvalue (locator value) represents an object that occupies some identifiable location in memory (i.e. has an address). rvalues are defined by exclusion. Every expression is either an lvalue or an rvalue, so, an rvalue is an expression that does not represent an object occupying some identifiable location in memory.
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’’ <=> rvalue
However for historical reasons I think "references not being part of C" could be a possible reason.
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