[julia-users] How do I create a function signature for a 2x2 matrix?

[Rick Muller]

I want to create a function signature for the *(a,b) operator where a is a 
2x2 matrix. Can I do this?

    *(a::Array{??,2},b) = whatever

??? is anything than can multiply a Complex vector. Do I have to explicitly 
promote this to Complex, in which case I guess it would be

   *(a::Array{Complex,(2,2)},b::Array{Complex,1}) = whatever

Thanks in advance for any help you can offer.