Hands-On Design Patterns and Best Practices with Julia

Differences between abstract and concrete types

Having discussed abstract types and concrete types, you may be wondering how they differ from each other. We can summarize their differences in the following table:

Property	Abstract Type	Concrete Type
Has a supertype?	Yes	Yes
Allows subtypes?	Yes	No
Contains data fields?	No	Yes
First class?	Yes	Yes
Can be part of a Union type?	Yes	Yes

 

For abstract types, we can build a hierarchy of types. The top-level type is just Any. Abstract types cannot contain any data fields as they are used to represent concepts rather than data storage. Abstract types are first-class, meaning that they can be stored and passed around, and there are functions that work with them—for example, the ...