Vector{AbstractString} function parameter won't accept Vector{String} input in julia

Question

The following code in Julia:

function foo(a::Vector{AbstractString})  
end
foo([\"a\"])

gives the following error:

ERROR:         


        

Answer 1

You need to write the function signature like this:

function foo{S<:AbstractString}(a::Vector{S})
    # do stuff
end

On Julia 0.6 and newer, it's also possible to write instead

function foo(a::Vector{<:AbstractString})
    # do stuff
end

This is a consequence of parametric type invariance in Julia. See the chapter on types in the manual for more details.