anonymous structs within structs

[DLearner]

On Tuesday, 5 December 2023 at 00:31:35 UTC, H. S. Teoh wrote:
> On Mon, Dec 04, 2023 at 11:46:45PM +0000, DLearner via 
> Digitalmars-d-learn wrote: [...]
>> Basically, B corresponds to the whole record (and only a whole 
>> record
>> can be read).
>> But the task only requires Var1 and Var2, the last two fields 
>> on the record.
>> By putting all the irrelevant fields into A, and defining B as 
>> above,
>> program remains unpolluted with data it does not need.
> [...]
>
> Sounds like what you need is something like this:
>
> 	struct Record {
> 		struct UnimportantStuff {
> 			...
> 		}
> 		UnimportantStuff unimportant;
>
> 		struct ImportantStuff {
> 			...
> 		}
> 		ImportantStuff important;
> 	}
>
> 	ImportantStuff readData() {
> 		Record rec = readData(...); // read entire record
> 		return rec.important; // discard unimportant stuff
> 	}
>
> 	int main() {
> 		...
> 		ImportantStuff data = readData(); // only important stuff 
> returned
> 		processData(data);
> 		...
> 	}
>
>
> T


I think that what you propose would work.

However, what I was really interested in was finding a way (using 
your example) of not instantiating UnimportantStuff anywhere.

Your suggestion instantiates it at:
```
UnimportantStuff unimportant;
```

I was thinking (again using your example) of something like:

```
    struct UnimportantStuff {
			...
	}

	struct Record {
		UnimportantStuff.sizeof;

		struct ImportantStuff {
			...
		}
		ImportantStuff important;
	}
```

But was concerned about possible alignment issues.