C++Talk.NET

edA-qa mort-ora-y · Guest

I've recently been using several enums for the purpose of loading/saving
data. What I've noticed would be quite helpful is a strongly typed
enum. I am sure this idea has been brought forward before, but I will
just add my viewpoint to it.

Basically given an enum:

enum Mode { One, Two, Three };

The old style of "just like an integer" can be kept for compatibility
and new operators introduced, or perhaps (as mentioned in the typedef
thread) use of an explicit keyword:

explicit enum Mode { One, Two, Three };

The "explicit" enum would then only allow assignment to/from an enum of
the same type. This of course requires a convesion operator, the
typical C cast could be used, but it might be cleaner to use a case like
syntax:

enum_cast<Mode>( 2 );

This would throw a "bad_cast" or "bad_enum" exception should the value
not be valid within the enum. Or perhaps have an option to assign a
default (but that might be too high-level logic for the standard).

-- --

The other aspect of this, which Java 1.5 seems to have added to their
new enums, is the ability to iterate over the enum values/names. For
this I propose that there is a template called enum_map, which is an STL
map of the name/values of the enum. Allowing something like this:

typedef enum_map<Mode> ModeMap;
for( ModeMap::iterator iter = ModeMap.begin();
iter != ModeMap.end(); iter++ )
cout << iter->first << "=" << iter->second << endl;

Where enum_map is a map of type map underlying type required for the enum.

An alternate, which wouldn't require this weird singelton/statis class
would be:

enum_map modeMap( Mode );

A fixed class enum_map that takes the Enum as a constructore.

--
edA-qa mort-ora-y (Producer)
Trostlos Records <http://trostlos.org/>

"What suffering would man know if not for his own?"

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