It's either the {::Tuple} or Array{Float64,}
You are using the first like you mean to say the function returns a tuple. This
is not what this means. In Julia, the return type is infered. Where you have
{::Tuple} is where you would put type parameters. For example,
function foobar{T<:Number}(x::Array{T,1})
...
end
This allows you to bypass the fact that Array{Int} is NOT a subtype of
Array{Number} because types are invariant in Julia.
The second possible culprit is the comma in Array{Float64,} has nothing after
it.
