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Re^2: shift vs @_

by BerntB (Deacon)
on Oct 03, 2006 at 09:21 UTC ( #576017=note: print w/ replies, xml ) Need Help??


in reply to Re: shift vs @_
in thread shift vs @_

Assume I have some large strings. I don't want them copied when I send them as parameters to subroutines/methods (which doesn't modify them).

Do I have to use the $_[x] notation for that? Should I send them in as references?


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Re^3: shift vs @_
by shmem (Canon) on Oct 03, 2006 at 20:50 UTC
    Both ways are ok. $_[0] is actually a reference (thanks, tye!) an alias to the first argument passed by the caller. You can evaluate (or operate on) $_[0] directly. Passing arguments as references just adds another level of indirection.

    You can also use prototypes for your subs and access your arguments inside the sub as references:

    #!/usr/bin/perl sub foo(\@\$) { warn "foo args: (".join(",",map{"'$_'"}@_).")\n"; print "1st argument = $_[0]; content =(" . join(',',map{"'$_'"} @{$_[0]}).")\n"; print "2nd argument = $_[1]; content = '".${$_[1]}."'\n"; my ($array,$scalar) = @_; push @$array, $$scalar; $$scalar = "blurf"; } my @ary = qw(foo bar baz); my $foo = "blah"; foo(@ary,$foo); print "ary: (@ary)\n"; print "foo: $foo\n";

    output:

    foo args: ('ARRAY(0x8167870)','SCALAR(0x8167978)') 1st argument = ARRAY(0x8167870); content =('foo','bar','baz') 2nd argument = SCALAR(0x8167978); content = 'blah' ary: (foo bar baz blah) foo: blurf

    --shmem

    _($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                                  /\_¯/(q    /
    ----------------------------  \__(m.====·.(_("always off the crowd"))."·
    ");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}
      $_[0] is actually a reference to the first argument passed by the caller.

      I'm sure you know what you meant, but... $_[0] is (usually) an alias to the first argument. If it were a reference then you'd have to use ${$_[0]} or such.

      - tye        

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