Hi Ingo-
The downside of the copy is that you lose
dataflow (and it takes more memory). I
can't test this out but you could use a
"throw away" copy to preserve dataflow:
eval { ($subset=$data->slice($b))->copy };
--Chris
On Thu, Aug 22, 2013 at 9:06 AM, Ingo Schmid <[email protected]> wrote:
>
> Thank you all for the helpful replies. This code did it for me:
>
> eval {$subset=$data->slice($b)->copy };
> if ($@) {
> message "Wrong Slice string $@" ,mb::Error;
> } else {
> ...
>
>
> Ingo
>
> On 08/21/2013 08:56 PM, David Mertens wrote:
>
> I'm not sure when a *bad* slice is caught, but an out-of-bounds slice is not
> caught until an actual evaluation. So, do a null operation, like adding zero
> in place. Note I use the eval { ... 1; } or do { ... }; idiom for exception
> handling, which I really like. It works just like a try/catch block, and is
> just as compact.
>
> my $slice;
> eval {
> $slice = $data->slice($string);
> $slice += 0;
> 1;
> } or do {
> croak("Bad slice string $string");
> };
>
> This conflates a malformed string and an out-of-bounds error, which may or
> may not be what you want. But hopefully it's a start.
>
> David
>
>
> On Wed, Aug 21, 2013 at 2:49 PM, Luis Mochan <[email protected]> wrote:
>>
>> I believe you are missing quotes. The argument of eval is a string to
>> be compiled and executed, as in
>> eval ('$y=slice ($x,"0,8,,")')
>> Regards,
>> Luis
>>
>>
>> On Wed, Aug 21, 2013 at 02:14:14PM +0000, Chris Marshall wrote:
>> > I don't have a working PDL but I mean using
>> > eval for exception trapping. Try looking at
>> > the eval docs in perldoc -f eval or someone with
>> > a working example....
>> >
>> > On Wed, Aug 21, 2013 at 1:51 PM, Ingo Schmid <[email protected]> wrote:
>> > > Chris,
>> > >
>> > > sorry, I get this. It never returns, just dies, apparently.
>> > >
>> > > pdl> help $x
>> > > This variable is Double D [2,6,1,4] P 0.38KB
>> > > pdl> eval (slice ($x,'0,8,,'))
>> > >
>> > >
>> > > Runtime error: Stringizing problem: Slice cannot start or end above
>> > > limit. eval {...} called at Basic/Core/Core.pm.PL (i.e.
>> > > PDL::Core.pm)
>> > > line 2969
>> > > PDL::string('PDL=SCALAR(0x4e242b0)', undef, '') called at (eval
>> > > 581)
>> > > line 5
>> > >
>> > >
>> > >
>> > > On 08/21/2013 03:36 PM, Chris Marshall wrote:
>> > >> eval ?
>> > >>
>> > >> On Wed, Aug 21, 2013 at 9:20 AM, Ingo Schmid <[email protected]> wrote:
>> > >>> Hi,
>> > >>>
>> > >>> I want a user to enter a string defining a slice of a piddle to
>> > >>> extract.
>> > >>>
>> > >>> Now when I call
>> > >>>
>> > >>>
>> > >>> $y=$x->slice($string) || barf "Not a valid slice\n";
>> > >>>
>> > >>> that does not catch it. How do I catch it?
>> > >>>
>> > >>> Ingo
>> > >>>
>> > >>> _______________________________________________
>> > >>> Perldl mailing list
>> > >>> [email protected]
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>> > >>>
>> > >
>> >
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>> --
>>
>> o
>> W. Luis Mochán, | tel:(52)(777)329-1734 /<(*)
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>>
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>
>
>
>
> --
> "Debugging is twice as hard as writing the code in the first place.
> Therefore, if you write the code as cleverly as possible, you are,
> by definition, not smart enough to debug it." -- Brian Kernighan
>
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