How can i get the value from an enum when passed to a function? For example i have the following code:

import std.stdio;

enum E : string
{
	one = "1",
	two = "2",
}

void print(E e)
{
	writefln("%s", e);
}

void main(string[] args)
{
	print(E.one);
}

The output is 'one'. How can i get at the value '1' instead. I could change the print function to accept a string like this:

void print(string e)
{
	writefln("%s", e);
}

but i lose the constraint of using an enum for the values.

On Sunday, 19 January 2014 at 17:37:54 UTC, Gary Willoughby wrote:
> How can i get the value from an enum when passed to a function? For example i have the following code:
>
> import std.stdio;
>
> enum E : string
> {
> 	one = "1",
> 	two = "2",
> }
>
> void print(E e)
> {
> 	writefln("%s", e);
> }
>
> void main(string[] args)
> {
> 	print(E.one);
> }
>
> The output is 'one'. How can i get at the value '1' instead. I could change the print function to accept a string like this:
>
> void print(string e)
> {
> 	writefln("%s", e);
> }
>
> but i lose the constraint of using an enum for the values.

You'll need to cast the value, but you can guard this cast using std.traits.OriginalType or write a toOType function.

auto toOType(E)(E e) if(is(E == enum)) { return cast(OriginalType!E) e; }

I never get these is-expressions right on first try, but the idea should be clear.

On Sunday, 19 January 2014 at 18:07:46 UTC, Tobias Pankrath wrote:
> You'll need to cast the value, but you can guard this cast using std.traits.OriginalType or write a toOType function.
>
> auto toOType(E)(E e) if(is(E == enum)) { return cast(OriginalType!E) e; }
>
> I never get these is-expressions right on first try, but the idea should be clear.

You don't have to use an explicit cast. Enum values can be implicitly converted to their base enum type:

---
string str = E.one;
writeln(str); // prints "1"
---

If DMD pull request #1356[1] is pulled, I think we'll be able to do:

---
writeln(string(E.one)); // prints "1"
---

I recommend avoiding the cast operator whenever possible.

[1] https://github.com/D-Programming-Language/dmd/pull/1356