重新定义受保护的符号和系统功能时遇到问题
发现尝试使用常用技巧 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>>
Found trying to use the usual trick to redefine 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>>
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评论（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< /a>.至少可以说，我不能说我喜欢这种语言功能。
When you run the redefinition the second time, it works fine. Most likely the cause of the problem is the same as discussed here. I can not say that I am fond of this language feature, to say the least.