possibility to check if a value belongs to an enumeration

[DarkDimius]

something like:

seg:
  - id: tag
    type: u1
  - id: etc
    if: enum_known.contains(tag)
enums:
  enum_known:
    1: utf8

[GreyCat]

Thanks for the suggestion!

The main problem here is that enums are not members, so it's impossible to call methods on them as is. Generally, object attributes (i.e. sequence attributes, instances, etc), types and enums are 3 different things and general abc syntax invokes only object attributes. We've kind of solve this problem with typecasting, so we need to invent some syntax to access enums as well.

There is currently only syntax element that concerns enums, and that is enum_name::enum_member, which resolves into EnumByName(...) AST expression, this, in turn, is translated into getting enum by name expression.

Any ideas?

[DarkDimius]

Given that there seems to be a plan to implement instanceOf checks, maybe this can be factored into those?

I.E, while tag.is<u1> will be checking type of data, tag.is<enum_known> will be checking if tag value belongs to range of values of enum_known.

[GreyCat]

I'm not really sure about instanceOf style checks now. The problem is that not all languages have some sort of RTTI. .NET CLR and JVM have them (albeit, as you know, JVM widely employs type erasure). C++ requires quite a few changes to enable RTTI, make classes properly virtual and enable stuff like typeid. C, if we'll ever support it, has absolutely no RTTI.

I like your proposal on checking syntax :)