Creating an array of user-defined structs

[Mike Parker via Digitalmars-d-learn]

On Monday, 22 August 2016 at 07:00:23 UTC, brian wrote:

>
> That's a terribly confusing naming convention for beginners 
> then! :P
> Is this D-specific terminology, or is this a more general 
> convention that AA are not actually arrays?
> This might help my understanding of when to use or not use one 
> or the other. :)

AA is an existing term and the concept is not specific to D (see 
the Wikipedia article [1]). Several other languages have them.

An AA is quite a distinct data structure from an array. Whereas 
arrays hold their items directly and tend to be laid out 
sequentially in memory (though they don't have to be), AAs do not 
and are not -- they might have linked lists, red-black trees or 
other data structures holding the items under the hood, all 
requiring the allocation of special nodes to associate meta data 
with each item. Arrays are indexed with sequential integers, AAs 
can be indexed with any properly configured key. It's only the 
read/write syntax in D that's similar, i.e. foo[key], though it 
didn't have to be that way. Take the [] syntax away from an AA 
and you might end up with something like the Java 
HashMap/HashTable or the C++ std::unordered_map. The name almost 
certainly derives from the [] syntax.

Because AAs and arrays distinct data structures (there are things 
you can do with one, but not the other), it's important to 
distinguish them in conversation.

[1] https://en.wikipedia.org/wiki/Associative_array