I wish to temporarily rename a built-in symbol and use it with different name while block the main name of this symbol. For example, I wish the following code to print only "2" but not "1" and "3":
Block[{print = Print, Print}, Print[1]; print[2]; Print[3];]
In really the above code prints nothing.
Is it possible to make print
working inside such code while completely block symbol Print
?
Solutions like
With[{Print = f, print = Print}, Print[1]; print[2]; Print[3];]
are not suitable since Print
is not really blocked inside such code.
The question appeared while thinking on a way to disable tracing of Message
internals.
This is not very clean, but I believe it is serviceable.
Internal`InheritedBlock[{Print},
Unprotect[Print];
Print[x__] := Null /; ! TrueQ[$prn];
print[x__] := Block[{$prn = True}, Print[x]];
Print[1]; print[2]; Print[3];
]
If it is not acceptable to have the function replaced with Null
in the return, you may need to use something like:
func[x__] := Hold[func[x]] /; ! TrueQ[$prn];
Followed by a ReleaseHold
after the Block.
Or:
func[x__] := zz[x] /; ! TrueQ[$prn];
and then follow the Block with: /. zz -> func
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