宏

julia> macro foo(arg)
           return arg+1
       end
@foo (macro with 1 method)
julia> @foo 9 # 有时需注意优先级
10
julia> @foo(9)
10

macro wrap(ty,sy::Symbol)
  return :($sy(i::$ty)=$sy(i.wr))
end
struct w wr end
@wrap w foo
foo(::Int)=1
println(foo(w(0)))