Enums - probably an old subject

[Daniel Kozak]

On Thursday, 21 November 2013 at 07:22:39 UTC, Steve Teale wrote:
> import std.stdio;
>
> enum Intention
> {
>    EVIL,
>    NEUTRAL,
>    GOOD,
>    SAINTLY
> }
>
> void foo(Intention rth)
> {
>    if (rth == EVIL)
>       writeln("Road to hell");
> }
>
>
> void main()
> {
>    foo(EVIL);
> }
>
>
> Why does the compiler complain in both places about EVIL. Can 
> it not work out which EVIL I mean? There's only one choice.

I don't think it would be a good idea to let a compiler decide 
which symbol I mean :). So you must use Intention.EVIL instead of 
just EVIL. Or you can do some trick like this:

enum Intention : int {_}
enum : Intention
{
     EVIL = cast(Intention)0,
     NEUTRAL = cast(Intention)1,
     GOOD = cast(Intention)2,
     SAINTLY = cast(Intention)3,
}

void foo(Intention rth)
{
     if (rth == EVIL)
         writeln("Road to hell");
}

void main()
{
     foo(EVIL);
}

or use aliases:

enum Intention
{
     EVIL,
     NEUTRAL,
     GOOD,
     SAINTLY,
}

alias EVIL = Intention.EVIL;
alias NEUTRAL = Intention.NEUTRAL;
alias GOOD = Intention.GOOD;
alias SAINTLY = Intention.SAINTLY;

void foo(Intention rth)
{
     if (rth == EVIL)
         writeln("Road to hell");
}

void main()
{
     foo(EVIL);
}