QVT13 — QVTo: multi-valued initialisation from single value

The two examples

mymultivaluedproperty += object Node

; // the list is reset and re-assigned

are simple assignments from single valued RHS. These are not covered in the preceding description.

I consider both to be errors since the RHS is unsuitable for assignment to the LHS. In both cases an asSet() or whatever should be appended.

More generally, the library operation that exhibits the "additive semantics" should be clearly identified.

Since addition to OCL collections is not permissible, it may be necessary to define constructors, so that

var c : Set(String) := Set

;

invokes the Set(T)(Set(T)) constructor.

This would allow initialization for a Sequence from a List and vice-versa that is otherwise magic.

Unclear multi-valued initialisation from single value

The two examples

mymultivaluedproperty += object Node

; // the list is reset and re-assigned

are simple assignments from single valued RHS. These are not covered in the preceding description.

I consider both to be errors since the RHS is unsuitable for assignment to the LHS. In both cases an asSet() or whatever should be appended.

More generally, the library operation that exhibits the "additive semantics" should be clearly identified.

Since addition to OCL collections is not permissible, it may be necessary to define constructors, so that

var c : Set(String) := Set

;

invokes the Set(T)(Set(T)) constructor.

This would allow initialization for a Sequence from a List and vice-versa that is otherwise magic.

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