Uninitialized arrays in Julia

Question

Say that I have an array of some composite type in Julia. I understand that I can't simply assign values into the array since its elements are undefined. For example the code

type struct
  u::Int64
  v::Int64
end

X = Array(struct, 100)
X[10].u = 3

will generate this error:

ERROR: access to undefined reference
 in getindex at array.jl:277
 in include at boot.jl:238
 in include_from_node1 at loading.jl:114

What is the standard way to deal with this? For now I am just doing something like:

samples = Array(Sample1d, num_samples)
fill!(samples, Sample1d(0, 0, 0))
samples[i] = ...

Is there a more concise or Julian way to do this?

Answer 1

You can use fill to create and fill an array at the same time:

type struct
  u::Int
  v::Int
end

struct() = struct(0, 0)
X = fill(struct(), 100)
X[10].u = 3