Value-based dispatch in Julia language

value_based_dispatch.jl

module ValueBasedDispatch

export MyType, A, B, C, f

abstract type MyType end
struct A <: MyType end
struct B <: MyType end
struct C <: MyType end

f(::Type{A}) = "Dispatch on argument A"
f(::Type{B}) = "Dispatch on argument B"
f(t::Type{T}) where T <:MyType = throw(DomainError("$(t)"))

end  

x.md

We can dispatch on the value types.

julia> f(A)
"Dispatch on argument A"
julia> f(B)
"Dispatch on argument B"
julia> f(C)
ERROR: DomainError with C:

Third-party code can extend MyType with new type D.

using ValueBasedDispatch

struct D <: MyType end
f(D) = "Dispatch on argument D"