When you want to store and look up the values based on a unique key, then the Dictionary type Dict (also called hash, associative collection, or map in other languages) is what you need. It is basically a collection of two-element tuples of the form (key, value). To define a dictionary d1 as a literal value, the following syntax is used:

// code in Chapter 5\dicts.jl:
d1 = [1 => 4.2, 2 => 5.3]

It returns Dict{Int64,Float64} with 2 entries: 2 => 5.3 1 => 4.2, so there are two key-value tuples here, (1, 4.2) and (2, 5.3); the key appears before the => symbol and the value appears after it, and the tuples are separated by commas. The [ ] indicates a typed dictionary; all the keys must have the same type, and the same is true for the values. A dynamic version of a dictionary can be defined with { }:

Any is also inferred when a common type among the keys or values...