Julia 1.0 Programming Complete Reference Guide

Mutating arrays

We can add more elements to the end of a collection by using the push! function:

julia> arr = [1, 2, 3] 
3-element Array{Int64,1}: 
 1 
 2 
 3 
julia> push!(arr, 4) 
4-element Array{Int64,1}: 
 1 
 2 
 3 
 4 
 
julia> push!(arr, 5, 6, 7) 
7-element Array{Int64,1}: 
  1 
  2 
  3 
  4 
  5 
  6 
  7 
 

Note the ending exclamation mark ! for the push! function. This is a perfectly legal function name in Julia. It is a convention to warn that the function is mutating—that is, it will modify the data passed as argument to it, instead of returning a new value.

We can remove elements from the end of an array using pop!:

julia> pop!(arr) 
7 
 
julia> arr 
6-element Array{Int64,1}: 
 1 
 2 
 3 
 4 
 5 
 6 

The call to the pop! function has removed the last element of arr and returned it.