Initialize an array of arrays in Julia

Sean Mackesey's answer will give you something of type Array{Array{T,N},1} (or Array{Array{Int64,N},1}, if you put the type in front of []). If you instead want something more strongly typed, for example a vector of vectors of Int (i.e. Array{Array{Int64,1},1}), use the following:

a = Vector{Int}[ [1,2], [3,4] ]

If you want an array of arrays as opposed to a matrix (i.e. 2-dimensional Array):

a = Array[ [1,2], [3,4] ]

You can parameterize (specify the type of the elements) an Array literal by putting the type in front of the []. So here we are parameterizing the Array literal with the Array type. This changes the interpretation of brackets inside the literal declaration.