Setting field of struct object

[Danilo]

On Monday, 22 January 2024 at 08:35:01 UTC, Joel wrote:
> I've lost interest in the video, looks like horrible syntax 
> (F#).

Nonetheless, this usually used with Objects (new class/struct 
instances), like so:
```d
import std;

struct Person {
     string name, email;
     ulong age;
     auto withName(string name) { this.name=name; return this; }
     auto withEmail(string email) { this.email=email; return this; 
}
     auto withAge(ulong age) { this.age=age; return this; }
}

void main() {
     auto p = (new Person).withName("Tom")
                          .withEmail("joelcnz at gmail.com")
                          .withAge(44);
     writeln(p);
}
```

If you convert it to a class, add an `static opCall` for 
initialization,
and a toString() method, it's even nicer:
```d
module app;

import std;

class Person {
     private string name, email;
     private ulong age;

     auto withName(string name) { this.name=name; return this; }
     auto withEmail(string email) { this.email=email; return this; 
}
     auto withAge(ulong age) { this.age=age; return this; }

     static Person opCall() => new Person();

     override string toString() {
         return "Person{ name: "~name~", age: "~age.to!string~", 
email: "~email~" }";
     }
}

void main() {
     auto p = Person()
                  .withName("Tom")
                  .withEmail("joelcnz at gmail.com")
                  .withAge(44);

     writeln(p);
}
```
It's common OOP style in some frameworks.