On Wed, Jun 17, 2020 at 11:50:27AM +0000, Per Nordlöw via Digitalmars-d-learn wrote: > Should a range-compliant aggregate type realizing a parser be encoded > as a struct or class?
Preferably a struct IMO, but see below. > In dmd `Lexer` and `Parser` are both classes. Probably for historical reasons. > In general how should I reason about whether an aggregate type should > be encoded as a struct or class? 1) Does it need runtime polymorphism? If it does, use a class. If not, probably a struct. 2) Does it make more sense as a by-value type, or a by-reference type? In several of my projects, for example, I've had aggregate types start out as structs (because of (1)), but eventually rewritten as (final) classes because I started finding myself using `ref` or `&` everywhere to get by-reference semantics. My rule-of-thumb is basically adopted from TDPL: a struct as a "glorified int" with by-value semantics, a class is a more traditional OO object. If my aggregate behaves like a glorified int, then a struct is a good choice. If it behaves more like a traditional OO encapsulated type, then a class is probably the right answer. T -- Many open minds should be closed for repairs. -- K5 user
