Re: "Value class instance" pattern?

[bearophile]

Dicebot:

Hm, actually naive scoped usage seems to work for me:
---------------------------------------
import std.typecons;

class B
{
        byte a;
}

class A
{
        typeof(scoped!B()) b = void;
        
        this()
        {
                b = scoped!B();
        }
}

Good. If I comment away most tags it seems to work:


import std.typecons;

const class Foo {
    int x;
    this(int xx) const pure nothrow {
        this.x = x;
    }
}

/*const*/ class Bar {
    /*const*/ typeof(scoped!Foo(1)) f = void;

    this(int x) /*const pure nothrow*/ {
        // f = typeof(f)(x); // Can't be used.
        f = scoped!Foo(x);
    }
}

void main() {
    auto b = new Bar(10);
}


I will try it in my code to see if and how well it works.


I have seen code like this:

class Bar {
    const int[1000] x = void;
    this(int n) {
        x[] = n;
    }
}
void main() {}



That gives me:

test.d(2): Warning: const field with initializer should be 
static, __gshared, or an enum
test.d(4): Error: slice x[] is not mutable


Are those error messages right?

Bye,
bearophile