无法重新定义受保护的符号和系统功能

Question

发现试图用来the usual trick重新定义GaussianFilter []:

out[x_]:=Print["(*"<>ToString@x<>"*)"];
(* Redefining Circle[ ] works as expected*)
Unprotect[Circle];
Circle[a_,args__]:=
      Block[{$i=True},{"Circle",a}]/;!TrueQ[$i];
Protect[Circle];
out@Circle[{0,1},1,{0,2Pi}]

(*{Circle, {0, 1}}*)

(* Redefining GaussianFilter[ ] does not*)
Unprotect[GaussianFilter];
GaussianFilter[a_,args__]:=
              Block[{$j=True},{"GaussianFilter",a}]/;!TrueQ[$j];
Protect[GaussianFilter];

SetDelayed::write: Tag GaussianFilter in GaussianFilter[a_,args__] is Protected>>

Answer 1

当您第二次运行重新定义时，它工作正常。问题的原因很可能与此处讨论的相同。至少可以说，我不能说我喜欢这种语言功能。