Rainer Deyke wrote:
Daniel Keep wrote:
It's not a bug. There are differences between value types and reference
types. Just like how there are differences between atomic types and
aggregate types. Or constant types and mutable types.
This is a bug:
struct MathematicalVector {
this(int size) {
this.values = new T[size];
}
// No copy constructor.
// Insert standard mathematical operators here.
private T[] values; // Implementation detail.
}
I want MathematicalVector to be a value type (which is why I declared it
as a struct). However, it doesn't behave a value type because I forgot
to write the copy constructor. D doesn't cause the bug, but it
certainly makes it easier to accidentally write this kind of bug.
By contrast, the compiler-generated copy constructors in C++ usually do
the right thing for all but a handful of low-level resource-management
classes. Which is not to say that C++ doesn't have problems of its own
- clearly it does, or I wouldn't be looking at D.
C++ ctors won't do the right thing if you use pointers, which is the
moral equivalent of using T[] inside MathematicalVector. If you refer to
std::vector instead, then that's a carefully-defined type that does have
the right copy constructor defined.
Andrei
