Is there a word that encompasses "classes" and "structs"?

Question

Classes and structs in C# share several characteristics:

• they can be instantiated (absent restrictions to the contrary, as with abstract and static classes)
• they can contain method and property implementations
• the type's author defines the type's instance fields

We often use "class" and "struct" to distinguish between "reference type" and "value type", but sometimes it's useful to consider both types of types. Furthermore, "reference type" also includes interfaces and delegates, which are not classes. So "class" doesn't mean any reference type, it means "a reference _(fill in the blank)_".

For example, if reference and value type declarations were like this:

public sealed class ref String { }
public class val Int32 { }

instead of like this:

public sealed class String { }
public struct Int32 { }

then the word "class" could be used to denote the concept.

The best answer I've come up with here is "concrete type", but that would be confusing, since it could also refer to the non-abstract subclass of an abstract class.

Any suggestions?

EDIT

To clarify, I'm not seeking a word that can collectively describe instances of classes and structs. I'm trying to describe class types and struct types.

In other words, if "class" denotes a set that includes System.String, System.FileInfo, etc., and "struct" denotes a set that includes System.Int32, System.Collections.Generic.List<T>.Enumerator, etc., then I'm looking for the word that denotes the union of those sets.

EDIT 2

(In reaction to Jordão's answer) Another way to answer this question would be to complete the following sentence: "All C# method implementations must be declared as members of a _(fill in the blank)_".

Answer 1

I realize this question has a selected answer, but I believe I can offer a fresh insight that will still be helpful:

I think the word you are looking for may be Model. This term is used to mean several different things in CS, but the wikipedia article for mathematical model describes my intension.

In this context, a model is a description of a system in some meta language. A system can be fully expressed in terms of its three parts: structure; behavior; and, interconnectivity. Both .NET classes and .NET structs are compatible with this definition. Interfaces are not, because the behavior is not defined. You can only indicate the structure of method calls and member declarations and the type contracts for operations (interconnectivity). Enums may or may not be compatible with this definition, but as most frequently used are not, because they typically do not express behavior. The exceptions are enums for which bitwise operations are sufficient representations of meaningful set operations. With this precondition, I think its fair to classify an enum along with classes and structs.

As a side note, both interfaces and standard enums could be considered as systems by themselves, if extension methods were interpreted as intrinsic to the types they extend. However, neither the compiler nor I would consider extension methods to be intrinsic to the type of the first operand. A more accurate interpretation would be to consider both the enum/interface and the extension method as necessary components of a system. The difference between these component types that are extended and a class/struct/special-case enum is that the class/struct/special-case enum is a system in-itself, and therefore a subsystem of its containing system, whereas the component type is a component but not a system in itself.

It is probably worthwhile to clarify that, under this interpretation, the term model is analogous to a type, whereas the term system is analogous to an instance. A system could also apply to a larger composite, such as an assembly, but that is not what the question was about.

The statement "All C# method implementations must be declared as members of a model" seems to work. It also does not logically entail that "all models can contain custom method implementations", so we are safe in the special-case of set-theoretic enums. It would also work in the case where the modeled system is the composition of static extension method implementations and interfaces.

 

Answer 2

The term type in C# can refer to any of:

• Reference Types
  • object, dynamic and string
  • Class types
  • Interface types
  • Delegate types
  • Constructed class/interface/delegate types (e.g. List<string>)
  • Array types
• Value types
  • Struct types
  • Enumeration types
  • Simple types (integral types, floating point types, decimal, and bool)
  • Nullable types
• Pointer types

All of these are terms from the C# specification.

class, interface, delegate, struct and enum types are also called type declarations (or: user-definable types).

Depending on your point of view, you might also consider type parameters and void to be types.

However, there isn't any special term for "classes or structs". In the language of the C# specification, one would say:

All C# method implementations must be declared as members of a class or struct declaration.

Answer 3

I find this to be a pseudo discussion. Point #3 can be said about enums and interfaces too, and the point about subclasses of abstract classes not fitting into the mix, I simply don't get. I think your own suggestion of "concrete types" is ok, but maybe you just want to talk about them as classes and structs, oh wait, but with the exception of subclasses of abstract classes and classes that implement interfaces. The reason that there is no term for what you are looking for might be that it is not a very useful concept in its own right.

EDIT:

All C# method implementations must be declared as members of a class or struct.

Answer 4

It should be Microsoft term. The origin of these notions is C++, where structs are just classes with all members being public. So, Microsoft cooked some new judging here, mixing some of C, C++ and Java. So they should invent also a terms.

Microsoft denotes them all as "types" which can be "value", "reference" and "pointer": http://msdn.microsoft.com/en-us/library/3ewxz6et(v=vs.100).aspx

But these notions do not gather only structs and classes.

So, if invent some custom term, we may take one from Pascal language, for example, where it is "record". Or some other terms can be coined from here: http://en.wikipedia.org/wiki/Object_composition

Answer 5

I normally use the term "type" to refer to any of those elements: class, struct and even interfaces and enums.

I never really felt the need to talk about classes and structs exclusively, I would probably just say "class", and then differentiate them as needed.

Answer 6

Both classes and structs are types which define objects. They are building blocks within an object oriented programming language. You can model both of them using UML or some other high-level object oriented modelling language. The choice between one or the other is an implementation detail.