Constructing an enum using the members of an AliasSeq as enumerator names
ag0aep6g via Digitalmars-d-learn
digitalmars-d-learn at puremagic.com
Wed Apr 27 08:30:55 PDT 2016
On 27.04.2016 13:06, Nordlöw wrote:
> /** Returns: a `string` containing the definition of an `enum` named
> `name` and
> with enumerator names given by `Es`, optionally prepended with
> `prefix` and
> appended with `suffix`.
>
> TODO Move to Phobos std.typecons
> */
> string makeEnumDefinitionString(string name,
> string prefix = `_`,
> string suffix = ``,
> Es...)()
> if (Es.length >= 1)
> {
> typeof(return) s = `enum ` ~ name ~ ` { `;
> foreach (E; Es)
> {
> s ~= prefix ~ E.stringof ~ suffix ~ `, `;
> }
> s ~= `}`;
> return s;
> }
>
> @safe pure nothrow @nogc unittest
> {
> import std.meta : AliasSeq;
> alias Types = AliasSeq!(byte, short);
> mixin(makeEnumDefinitionString!("Type", `_`, `_`, Types));
> static assert(is(Type == enum));
> static assert(Type._byte_.stringof == "_byte_");
> static assert(Type._short_.stringof == "_short_");
> }
>
> Can it be made more elegant?
I'd hide the string mixin in the template:
----
template makeEnumFromSymbolNames(string prefix = `_`,
string suffix = ``,
Es...)
if (Es.length >= 1)
{
enum members = {
string s = "";
foreach (E; Es)
{
s ~= prefix ~ E.stringof ~ suffix ~ `, `;
}
return s;
}();
mixin("enum makeEnumFromSymbolNames {" ~ members ~ "}");
}
@safe pure nothrow @nogc unittest
{
import std.meta : AliasSeq;
alias Types = AliasSeq!(byte, short);
alias Type = makeEnumFromSymbolNames!(`_`, `_`, Types);
static assert(is(Type == enum));
static assert(Type._byte_.stringof == "_byte_");
static assert(Type._short_.stringof == "_short_");
}
----
The `foreach` could be replaced with `map` and `joiner`, but I'm not
sure if that would be an improvement.
`format` might be interesting:
----
import std.format;
import std.meta: staticMap;
enum stringOf(t...) = t[0].stringof;
mixin(format(
"enum makeEnumFromSymbolNames {%-(" ~ prefix ~ "%s" ~ suffix
~"%|, %)}",
[staticMap!(stringOf, Es)]
));
----
That takes longer to compile, though. Probably needs more memory as well.
More information about the Digitalmars-d-learn
mailing list