[julia-users] Passing Array{Array{T,N},1} to a function

[Alan Crawford]

I would like to preallocate memory of an array of arrays and pass it to a 
function to be filled in. I have created an example below that illustrates 
my question(s).

Based on my (probably incorrect) understanding that it would be desirable 
to fix the type in my function, I would like to be able to pass my array of 
arrays, X, in a type stable way.  However, I can't seem to pass 
Array{Array{Float64,N},1}. If, however, i do not attempt to impose the type 
on the function, it works. 

Is there a way to pass Array{Array{Float64,N},1 to my function? Do I even 
need to fix the type in the function to get good performance?

# version of Julia: 0.4.0-rc3

@generated function 
testfun1!{N}(X::Array{Array{Float64,1},1},Y::NTuple{N,Float64})
quote
for j in 1:$N, i in eachindex(X)
X[i][j] = Y[j]
end
return X
end
end

@generated function testfun2!{N}(X,Y::NTuple{N,Float64})
quote
for j in 1:$N, i in eachindex(X)
X[i][j] = Y[j]
end
return X
end
end

# Setup for function call
InnerArrayPts = 3
OuterArrayPts = 10
Xinput = [Array{Float64}(InnerArrayPts) for r in 1:OuterArrayPts]
Yinput = rand(InnerArrayPts)

# Method Error Problem
testfun1!(Xinput,tuple(Yinput...))

# This works
testfun2!(Xinput,tuple(Yinput...))

I also tried with the following version of testfun1!() and again got a 
method error.

@generated function 
testfun1!{N}(X::Array{Array{Float64,N},1},Y::NTuple{N,Float64})
quote
for j in 1:$N, i in eachindex(X)
X[i][j] = Y[j]
end
return X
end
end


I am sure i am misunderstanding something quite fundamental and/or missing 
something straightforward...

Thanks,
Alan