Re: [julia-users] What is the correct way to use the type alias Vector and Matrix in multiple dispatch?

[Yichao Yu]

On Wed, Apr 6, 2016 at 4:23 PM, Po Choi <vegetableb...@gmail.com> wrote:
>
> hello(A::Matrix) = 1
> hello(A::Vector{Matrix}) = 2

http://julia.readthedocs.org/en/latest/manual/types/#parametric-composite-types

Vector{Matrix{Float64}} is not a subtype of Vector{Matrix}

> A = randn(3,3);
> AA = [randn(3,3) for k in 1:4];
> hello(A)
> hello(AA)
>
> The output has method error.
> julia> hello(A)
> 1
>
> julia> hello(AA)
> ERROR: MethodError: `hello` has no method matching
> hello(::Array{Array{Float64,2},1})
>
>
> If I write down the types explicitly,
> hi(A::Array{Float64,2}) = 1
> hi(A::Array{Array{Float64,2},1}) = 2
> A = randn(3,3);
> AA = [randn(3,3) for k in 1:4];
> hi(A)
> hi(AA)
> The output is what I expect.
> julia> hi(A)
> 1
>
> julia> hi(AA)
> 2
>
> Am I using Vector and Matrix in a wrong way?