On Saturday, 17 August 2013 at 05:22:53 UTC, captaindet wrote:
import std.stdio;
enum Test{
test2 = 2,
test4 = 4
}
Enumeration.
enum foo = Test.test2;
Manifest Const
Test bar = Test.test4;
Runtime variable.
Enum is being abused. In the first case you are declaring an
enumeration[1], these values are known at compile time.
Second you defined a manifest constant, this is what you would
see from #define in C. The symbol, foo, is replaced by the right
hand side when referenced.
Third you've declared a variable, bar, which will store your
enumerated value, 4. Variables are not compile time, even if the
value stored came from a compile time known value.
int foobar = 5; // 5 is known at compile time, foobar is not.
pragma( msg, foo ); // why does it print: cast(Test)2
You are referring to a manifest constant, this is a simple
textual replacement. Enumerations are typed, 2 is not a Test, so
the compiler will write out a cast so the type system is happy.
Similarly Test.test2 is not the value of foo, foo is a signal to
the compiler to insert "cast(Test)2."
Hope that makes sense.
1. http://en.wikipedia.org/wiki/Enumeration
