Re: [Boston.pm] something about @_ is different?

Ugh. I dont like this.

Its linguistically inconsistent.
Assign to an element in array assigns back to caller var.
Assign to whole array disconnects the aliases
that ties @_ back to the caller vars and assigns to a local version of @_?

If someone wants to disconnect the underlying aliases,
call local() and put the syntactic sugar there.

And then assigning to @_ without local() would work just
like assigning to all the individual elements in array.

Perl can be disappointing sometimes.

Greg



On Tue, May 21, 2019 2:12 pm, Conor Walsh wrote:
> Assigning to @_ is weird and I don't recommend it. It's full of magic
> aliases, which in some cases means you change the caller's variables,
> which is usually not what you want.
>
> Check the beginning of perldoc perlsub.
>
>
> On Tue, May 21, 2019, 2:04 PM Greg London <email-2Ro/Dj86MvDSUeElwK9/[email protected]> wrote:
>
>
>>
>> Hm, it could be a caffeine defficiency, but it seems that @_ is
>> being treated different than other arrays.
>>
>> I can create a normal array:
>> my @normal_array=('a','b');
>>
>> and I can assign an entirely new list to it:
>> @normal_array=reverse(@normal_array);     # assign to array
>>
>>
>> and I can assign to it in parenthesis an entirely new list
>> (@normal_array)=reverse(@normal_array);   # assign to (array)
>>
>>
>>
>> And those assignements take hold as I would expect.
>>
>>
>> When I use the exact same syntax for the @_ array instead
>> of @normal_array, it doesn't work as expected: sub swapper{ (@_) =
>> reverse(@_);  # this doesn't seem to do anything. }
>>
>>
>> my @other=('x','y'); swapper(@other); print Dumper \@other;
>>
>> Pretty sure this code used to work,
>> but that was many moons ago.
>>
>> Thoughts?
>>
>>
>> Greg
>>
>>
>> Here's the script in one big copy/paste block:
>>
>>
>>
>> my @normal_array=('a','b'); print "normal_array is "; print Dumper
>> \@normal_array;
>> @normal_array=reverse(@normal_array);     # assign to array
>> print "normal_array is "; print Dumper \@normal_array;
>> (@normal_array)=reverse(@normal_array);   # assign to (array)
>> print "normal_array is "; print Dumper \@normal_array;
>>
>>
>> sub swapper{ (@_) = reverse(@_);
>> }
>>
>>
>> my $one = "i am one"; my $two = "i am two";
>>
>> swapper($one,$two);
>>
>> warn "one is '$one'"; warn "two is '$two'";
>>
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>>
>>
>


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