On 4/9/14, 8:44 AM, Benjamin Thaut wrote:
Am 08.04.2014 21:08, schrieb Andrei Alexandrescu:
(moving http://goo.gl/ZISWwN to this group)
On 4/7/14, 3:41 PM, w0rp wrote:
Yeah, I've seen this happen before. I think we could actually introduce
a little more type safety on enums without a great deal of breakage. It
would be nice to have a final switch give you as much of a guarantee
about what it's doing as it can.
People use enums for things such as:
1. A discrete set of categorical values:
enum State { initial, waiting, running, done }
That's probably the most common use, and the one that prompted the
moniker "enum(eration)".
This seems to be exactly the use case for which C++ enum class has been
designed. But there is one major flaw in C++ enum class. Usually if you
have a discrete set you want to use it to index into an array.
E.g.
enum ShaderType { Vertex, Geometry, Pixel };
Shader[ShaderType.max] shaders;
shaders[ShaderType.Vertex] = new Shader();
In C++ you can't index arrays using a enum class without casting them
first. This is in my opinion a major problem. We should not make the
same mistake, in case we redesign enums.
Very true. In hhvm, we tried an enum class to avoid bugs with using
wrong indices in a couple of specific arrays. There were so many darned
casts around, we had to revert the change.
Andrei
