How to abort evaluation of a sequence of inputs?
By default pressing Alt+. or calling Abort[]
within the evaluation causes abort of the currently evaluating input. But when working in the FrontEnd we usually send to the kernel a sequence of inputs. For example, if we type the following three expressions on separate lines in one Cell
and then press Shift+Enter we get infinite evaluation:
f := CheckAbort[Pause[.1], Abort[]]
While[True, f]
While[True, f]
While[True, f]
To stop this开发者_JAVA技巧 infinite evaluation we must to press Alt+. three times.
How to define the function f
in the example above in such a way that pressing Alt+. one time will abort the evaluation of the full sequence of inputs without quitting the kernel?
EDIT
I think that if the FrontEnd creates an input queue for MathKernel it probably can also cancel this queue.
Sasha's suggestion to just use four cells is valid, because that's basically what the FrontEnd does anyway, submitting several distinct evaluations to the Kernel. If you insist in using one cell, wrap it in parens (CompoundExpression
), which causes those four lines to be treated as one evaluation (note the need for ;
too):
(
f := CheckAbort[Pause[.1], Abort[]];
While[True, f];
While[True, f];
While[True, f]
)
Then, one abort issued will abort the evaluation as a whole.
I have found a way to do what I want. The only problem is that at this moment I do not know how to check whether the FrontEnd has some pending inputs. I am forced just to wait 1 second. In the most cases it is sufficient time for sending all pending inputs to the kernel but probably not always.
In[1]:= $new$PreRead = False;
AbortAllPendingInputs :=
AbortProtect[If[! $new$PreRead, $new$PreRead = True;
$TimeOfAbort = SessionTime[];
last$PreRead = ToString[Definition[$PreRead], InputForm];
ClearAll[$PreRead];
$PreRead := If[TrueQ[SessionTime[] - $TimeOfAbort < 1], "",
$new$PreRead = False;
ClearAll[$PreRead];
If[last$PreRead === "Null", #,
ToExpression[last$PreRead]; $PreRead@#]
] &;]];
In[3]:= f := CheckAbort[Pause[10], AbortAllPendingInputs; Abort[]]
In[4]:= While[True, f]
While[True, f]
While[True, f]
Out[4]= $Aborted
But I am still looking for more elegant solution. I think that if the FrontEnd creates an input queue for MathKernel it probably can also cancel this queue.
Alexey, please try this version of your code and tell me if/when it fails:
AbortAllPendingInputs :=
AbortProtect[
$new$PreRead = True;
$TimeOfAbort = SessionTime[];
last$PreRead = $PreRead;
$PreRead =
If[
TrueQ[SessionTime[] - $TimeOfAbort < 1],
"",
$new$PreRead = False; $PreRead = last$PreRead; $PreRead[#]
] &;
] /; ! TrueQ[$new$PreRead]
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