带有符号的通用调度

Question

我想知道是否有一种方法可以使用 Symbols 进行多次分派，而且还包括一个 "catch-all method"。即类似

function dispatchtest{alg<:Symbol}(T::Type{Val{alg}})
  println("This is the generic dispatch. The algorithm is $alg")
end
function dispatchtest(T::Type{Val{:Euler}})
  println("This is for the Euler algorithm!")
end

第二个有效并且与手册中的内容相匹配，我只是想知道你是如何让第一个有效的。

Answer 1

你可以这样做：

julia> function dispatchtest{alg}(::Type{Val{alg}})
           println("This is the generic dispatch. The algorithm is $alg")
       end
dispatchtest (generic function with 1 method)

julia> dispatchtest(alg::Symbol) = dispatchtest(Val{alg})
dispatchtest (generic function with 2 methods)

julia> function dispatchtest(::Type{Val{:Euler}})
           println("This is for the Euler algorithm!")
       end
dispatchtest (generic function with 3 methods)

julia> dispatchtest(:Foo)
This is the generic dispatch. The algorithm is Foo

julia> dispatchtest(:Euler)
This is for the Euler algorithm!

带有符号的通用调度

Generic dispatch with Symbols

julia

multiple-dispatch