struct vs class for a simple token in my d lexer

[Jonathan M Davis]

On Monday, May 14, 2012 17:10:23 Roman D. Boiko wrote:
> (Subj.) I'm in doubt which to choose for my case, but this is a
> generic question.
> 
> http://forum.dlang.org/post/odcrgqxoldrktdtarskf@forum.dlang.org
> 
> Cross-posting here. I would appreciate any feedback. (Whether to
> reply in this or that thread is up to you.) Thanks

For the question in general, there are primarily 2 questions to consider:

1. Do you need inheritance/polymorphism?

2. Do you need a value type or a reference type?

If you need inheritance/polymorphism, you have to use classes, because structs 
don't have inheritance.

If you want a value type, you have to use structs, because classes are 
reference types.

If you want a reference type, then you can use either a class or a struct, but 
it's easier with classes, because classes are always reference types, whereas 
structs are naturally value types, so it can take more work to make them 
reference types depending on what its member variables are.

One other thing to consider is deterministic destruction. The only way to get 
deterministic destruction is to have a struct on the stack. Value types will 
naturally get that, but if you want a reference type with determinstic 
destruction, then you're probably going to have to use a ref-counted struct.

In the vast majority of cases, that should be enough to decide whether you 
need a class or a struct. The main case that it doesn't is the case where you 
want a reference type and don't necessarily want a class, and that decision 
can get complicated.

In the case of a token in a lexer, I would definitely expect that to be a value 
type, which means using a struct.

- Jonathan M Davis