An array can take elements of different types. Therefore, we can have, for example, arrays of the following types: Array{Int64,1}, Array{Int8,1}, Array{Float64,1}, or Array{String, 1}, and so on. That is why an Array is a parametric type; its elements can be of any arbitrary type T, written as Array{T, 1}.
In general, types can take type parameters, so that type declarations actually introduce a whole family of new types. Returning to the Point example of the previous section, we can generalize it to the following:
# see the code in Chapter 6\parametric.jlmutable struct Point{T} x::T y::Tend
This is conceptually similar to the generic types in Java or templates in C++.
This abstract type creates a whole family ...
