> -----Original Message-----
> From: nkuipers [mailto:[EMAIL PROTECTED]]
> Sent: Tuesday, July 23, 2002 2:13 AM
> To: [EMAIL PROTECTED]
> Subject: RE: How to make @array2 use values of @array1?
>
>
> What I am about to raise, I do so more out of wanting someone
> to educate me
> than disagreeing for the sake of. The *that syntax shown
> below is unfamiliar
> to me outside the context of referencing a filehandle in a
> subroutine params
> list, where it is optional (ie., &some_sub(*STDIN)).
See perldoc perldata, under the heading "Typeglobs and Filehandles",
and perldoc perlmod, under the heading "Symbol Tables"
> *that
> reminds me an
> awful lot of a C pointer, however. Can someone clear this up for me?
>
> I found the following in the Camel 3rd edition, page 257,
> which, though I may
> be wrong, looks like it does what is requested?
>
> @reflist = \(@x); #interpolate array, then get refs
>
> which looks an awful lot like
>
> @array2 = \(@array1);
Right, but it's a lot different than
*array2 = \@array1;
The first syntax:
@array2 = \(@array1)
is distributing the reference operation over each element of @array1
and assigning those references to @array2. Fire up your perl debugger
and try the following:
$ perl -d -e 1
Default die handler restored.
Loading DB routines from perl5db.pl version 1.07
Editor support available.
Enter h or `h h' for help, or `man perldebug' for more help.
main::(-e:1): 1
DB<1> @array1 = qw(foo bar baz)
DB<2> @array2 = \(@array1)
DB<3> x @array2
0 SCALAR(0x80f82dc)
-> 'foo'
1 SCALAR(0x82c7e64)
-> 'bar'
2 SCALAR(0x82c7ca8)
-> 'baz'
DB<4>
So you can see that each entry in @array2 is a reference to the
corresponding entry in @array2.
Now, try the other syntax:
DB<4> *array2 = \@array1
DB<5> x @array2
0 'foo'
1 'bar'
2 'baz'
DB<6> x \@array1, \@array2
0 ARRAY(0x82c7ce4)
0 'foo'
1 'bar'
2 'baz'
1 ARRAY(0x82c7ce4)
-> REUSED_ADDRESS
DB<7>
So, *array2 = \@array1 makes the name @array2 and alias for @array1,
i.e. they are two names for the same data (at address 0x82c7ce4 in
the example above).
HTH
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