Initialize array of objects not work

[Ali Çehreli via Digitalmars-d-learn]

On 08/03/2016 10:58 AM, Andre Pany wrote:

 > I try to initialize an array of objects. The methods (linear/equals/....)
 > returns object of different classes, but all implement a common
 > interface "Element".
 >
 > Element[] elements =
 > quadraticCoefficient(1)~linearCoefficient(2)~equals()~constant(1);

Note that those array concatenation operators are being applied to 
individual object. Unless you define that operator for your types, it 
won't work.

 > I tried different casts and different ways but it seems, currently D
 > does not support this syntax?

Not that syntax but D is supposed to figure out the closest common 
ancestor. Unfortunately, the following code requires that cast:

interface Element {
}

class Foo : Element {
}

class Bar : Element {
}

Foo quadraticCoefficient(int) {
     return new Foo();
}

Bar linearCoefficient(int) {
     return new Bar();
}

Foo equals() {
     return new Foo();
}

Bar constant(int) {
     return new Bar();
}

void main() {
     Element[] elements = cast(Element[])[ quadraticCoefficient(1), 
linearCoefficient(2), equals(), constant(1) ];
     elements ~= quadraticCoefficient(1);
     elements = elements ~ linearCoefficient(2);
     // etc.
}

Ali