As far as I'm aware, there are two nice ways to tell the comprehension the
type that is going to be returned.
Option 1: Tell it the type of the comprehension:
K = Float64[dot(X[:,i], X[:,j]) for i=1:5, j=1:5]
Option 2: Assert the type of the return of "dot"
K = [dot(X[:,i],X[:,j])::Float64 for i=1:5, j=1:5]
As far as I can tell, they'll do the same thing.
On Tuesday, 10 November 2015 02:37:17 UTC+10, rizal zaini wrote:
>
> Hi all
>
> I want to create matrix containing dot products
>
> julia> X = rand(5,5)
> 5x5 Array{Float64,2}:
> 0.274799 0.564619 0.915595 0.341059 0.57361
> 0.0806822 0.293939 0.379279 0.608582 0.652441
> 0.264678 0.532751 0.289088 0.457759 0.492777
> 0.33856 0.495587 0.499099 0.548237 0.402534
> 0.686305 0.168385 0.8322 0.605532 0.518693
>
> julia> K = [dot(X[:,i], X[:,j]) for i=1:5, j=1:5]
> 5x5 Array{Any,2}:
> 0.737716 0.603229 1.09884 0.865174 0.832958
> 0.603229 0.962978 1.16994 0.988988 1.06501
> 1.09884 1.16994 2.00739 1.45298 1.54767
> 0.865174 0.988988 1.45298 1.36347 1.35304
> 0.832958 1.06501 1.54767 1.35304 1.42861
>
> I expect to get an Array{Float64,2}, but what I got is Array{Any,2}.
> How to get Array{Float64,2} using Array comprehension?
>
> Thanks before
> Rizal
>
