Dictionaries

The dictionary, called Dict, is one of Julia's most powerful and versatile data structures. It's an associative collection—it associates keys with values. You can think of a Dict as a look-up table implementation—given a single piece of information, the key, it will return the corresponding value.

Constructing dictionaries

Creating an empty instance of a Dict is as simple as the following:

julia> d = Dict() 
Dict{Any,Any} with 0 entries

The information between the curly brackets, {Any,Any}, represents the types of keys and values of the Dict. Thus, the concrete type of a Dict itself is defined by the type of its keys and values. The compiler will do its best to infer the type of the collection from the types of its parts. In this case, since the dictionary was empty, no information could be inferred, so Julia defaulted to Any and Any.

An {Any,Any} type of Dict allows us to add any kind of data, indiscriminately. We can use the setindex! method to add a new key-value pair to the...