Stack
Union{Types...}
A type union is an abstract type which includes all instances of any of its argument types. The empty union Union{}
is the bottom type of Julia.
Examples
julia> IntOrString = Union{Int,AbstractString}
Union{Int64, AbstractString}
julia> 1 isa IntOrString
true
julia> "Hello!" isa IntOrString
true
julia> 1.0 isa IntOrString
false