An Enumap is a glorified wrapper around a static array.
Are you sold yet? No? Alright, take a look at this:
enum Attribute {
strength, dexterity, constitution, wisdom, intellect, charisma
}
Now you want to map each Attribute to an int.
You could use D's built-in associative arrays:
int[Attribute] attributes;
attributes[Attribute.strength] = 10;
However, I think you'll like Enumap better:
Enumap!(Attribute, int) attributes;
attributes[Attribute.strength] = 10;
Still not impressed? Well, you might prefer an Enumap if:
You like syntactic sugar:
// Boring!
if (hero.attributes[Attribute.wisdom] < 5) hero.drink(unidentifiedPotion);
// Fun! And Concise!
if (hero.attributes.wisdom < 5) hero.drink(unidentifiedPotion);
You like ranges:
// roll for stats!
attributes = generate!(() => uniform!"[]"(1, 20)).take(6);
You like default values:
int[Attribute] aa;
Enumap!(Attribute, int) em;
aa[Attribute.strength]; // Range violation!
em.strength; // 0
You like array-wise operations:
// note the convenient constructor function:
auto bonus = enumap(Attribute.charisma, 2, Attribute.wisdom, 1);
// level up! adds 2 to charisma and 1 to wisdom.
hero.attributes += bonus;
You dislike garbage day:
void donFancyHat(ref int[Attribute] aa) { aa[Attribute.charisma] += 1; }
@nogc void donFancyHat(ref Enumap!(Attribute, int) map) { map.charisma += 1; }
Check the docs for the full feature set.
Enumap comes in dub package form.