Re^2: Modifying a parameter to a recursive function

While your points are definitely good advice, I'm not sure that's what he's asking about. I think the OP is asking about modifying the parameters to the subroutine in-place. For example:

@a = (1..10);

sub x {
    foreach (@_) {
        $_++;
    }
}

x(@a);

print @a;  #prints 234567891011
[download]

So in principle, you can modify a subroutine's arguments using the default variable $_ inside a foreach loop. Question is, why isn't it working inside his recursive function?

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Re^3: Modifying a parameter to a recursive function by GrandFather (Saint) on Apr 08, 2009 at 21:42 UTC
I don't think that is really the OP's problem. What you suggest can be checked trivially by: `use strict; use warnings; my @array = (1 .. 8); print "Before: @array\n"; nastyModifyParamsSub (@array); print "After: @array\n"; sub nastyModifyParamsSub { for my $element (@_) { ++$element; } }` [download] Prints: `Before: 1 2 3 4 5 6 7 8 After: 2 3 4 5 6 7 8 9` [download] Which shows that modifying the parameters is possible and that there is nothing magical about requiring $_ to do it. The following though shows one way that OP's code could be going awry: `use strict; use warnings; my @array = (1 .. 8); print "Before: @array\n"; nastyModifyParamsSub (@array); print "After: @array\n"; sub nastyModifyParamsSub { for (@_) { ++$_; clobberDefVar (); } } sub clobberDefVar { $_ = 0; }` [download] Prints: `Before: 1 2 3 4 5 6 7 8 After: 0 0 0 0 0 0 0 0` [download] The bottom line though to that the OP's description is an fuzzy unclear thing and there is too much code and no data at all. True laziness is hard work	[reply] [d/l] [select]
Re^4: Modifying a parameter to a recursive function by ikegami (Patriarch) on Apr 08, 2009 at 21:53 UTC
I'm trying to see it your way, but I don't see where you think there's an unlocalized `$_`. `tag` and `content_list` could theoretically clobber `$_`, but you'd figure that subsequent method calls would fail if they did.	[reply] [d/l] [select]