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
