enum scope

[Meta via Digitalmars-d]

On Thursday, 26 January 2012 at 13:23:43 UTC, Trass3r wrote:
>> It's not type safe in C. But you can wrap it in a struct with 
>> alias this instead.
>
> Yep, but in D we have strong enums, so why not use them.

Enums aren't as strongly typed as you would think (or as I would 
like). The major problem is that it's incredibly easy to get an 
invalid enum value, even without using a cast.

enum Foo
{
     one = 1,
     two,
     three,
}

enum Bar
{
     first,
     second,
     third,
}

void takesFoo(Foo foo)
{
}

void main()
{
     int n = Foo.one;
     assert(n == 1);
	
     //Luckily, this doesn't compile
     //Foo foo1 = n;

     int[] arr = new int[](3);
     int m = arr[Foo.two];
	
     //Unfortunately, this DOES compile
     Foo foo2 = Foo.one - Foo.two;
     assert(foo2 == -1);
     takesFoo(foo2);
	
     //Fails (thank goodness)
     //takesFoo(Bar.third);
	
     //This actually isn't as bad as it looks.
     //The result is of type int and thus
     //can't be assigned back to a Foo or Bar
     assert(Foo.two - Bar.third == 0);
	
     //Fails
     //Foo foo3 = Foo.two - Bar.second;
	
     //Fails
     //Bar bar = Bar.first - Foo.three;
}