Julia: @generated=>多姿多彩！

Julia doc 关于 @generated:
A very special macro is @generated, which allows you to define so-called generated functions. These have the capability to generate specialized code depending on the types of their arguments with more flexibility and/or less code than what can be achieved with multiple dispatch. While macros work with expressions at parsing-time and cannot access the types of their inputs, a generated function gets expanded at a time when the types of the arguments are known, but the function is not yet compiled.

方便吧！

@generated function bar(x) # 没有@generated会报错
          if x <: Integer
              return :(x^2)   # 注意，：表示quoted expression,不能少！
          elseif x<:AbstractString
              return :(string(x,", hello world!")) # 注意，不能少“：”
          else 
              return :(x*3) # 注意，不能少“：”
          end
      end

有趣吧！

       dat1 =bar(5.0) # 15.0
       dat2 =bar(5)   # 25
       dat3 =bar("wo")# wo,hello world