Forget splice

sub p {
# my($c,$s,@x)=@_;my@a=($s)x(-@x+abs$c);$c>0?(@x,@a):(@a,@x)
($*,$^,@#)=@_;@*=($^)x(-@#+abs$*);$*>0?(@#,@*):(@*,@#)
#234567890123456789012345678901234567890123456789012345678
}
[download]

(Added) A word of explanation. If the multiplier is zero or negative, ($foo) x $bar returns an empty list. Punctuation variables are a vile trick.

With slightly easier to read vars:

sub p{($a,$b,@_)=@_;@*=($b)x(-@_+abs$a);$a>0?(@_,@*):(@*,@_)}
[download]

Also the prototype of abs makes this annoying, i thought you could reorder the -@_+abs$a to lose one of the operators but the abs() then requires parens. Nice one by the way. :-)

---
demerphq

This is a natural for splice,

sub p{
my($c,$s,@x)=@_;abs$c>@x&&splice@x,$c>0?@x:0,0,($s)x(-@x+abs$c);@x
#234567890123456789012345678901234567890123456789012345678901234567
}
[download]

#Returns a copy of the input padded to size specified by pad_size with
+ value pad_value.
#If pad_size is positive then the array is padded on the right, if it'
+s negative then on the left.
#If the absolute value of pad_size is less than or equal to the length
+ of the input then no padding takes place.
#int pad_size, mixed pad_value, array  input

sub array_pad{
    my($pad_size, $pad_value, @array) = @_;
    #this is just to get the absolute value of the pad_size
    my $temp = $pad_size;
    if($pad_size < 0){
        $temp = $temp * -1;
    }#if
    #first let's see if the pad_size is less than or equal to the arra
+y size, return 0 no padding
    my $input_size = @array;
    if($temp <= $input_size){
        return 0;
    }#if
    #since it didn't return 0, time to pad
    #if the pad_size is < 0, pad on the left, else the right
    if($pad_size < 0){
        my @retval;
        $temp = $temp - $input_size;
        for(my $i=0;$i<$temp;$i++){
            unshift(@array, $pad_value);
        }#for
        return @array;
    }#if
    else{
        $temp = $pad_size - $input_size;
        for(my $i=0;$i<$temp;$i++){
            push(@array, $pad_value);
        }#for
        return @array;
    }#else
}#array_pad

sub p{my($i,$z,@f)=@_;abs$i>@f&&$i<0?@f=(($z) x abs($i+@f),@f):(@f[@f.
+.$i-1]=($z)x($i-@f));@f}

use Test::More tests => 4;

my @x = 1 .. 5;

is_deeply([p( 3, 'x', @x)], [array_pad( 3, 'x', @x)]);
is_deeply([p(-3, 'x', @x)], [array_pad(-3, 'x', @x)]);
is_deeply([p( 7, 'x', @x)], [array_pad( 7, 'x', @x)]);
is_deeply([p(-7, 'x', @x)], [array_pad(-7, 'x', @x)]);

__END__
1..4
not ok 1
#     Failed test (golfing.array_pad.pl at line 43)
#     Structures begin differing at:
#          $got->[0] = '1'
#     $expected->[0] = '0'
not ok 2
#     Failed test (golfing.array_pad.pl at line 44)
#     Structures begin differing at:
#          $got->[0] = '1'
#     $expected->[0] = '0'
ok 3
ok 4
# Looks like you failed 2 tests of 4.
[download]

Congratulations, you've found one of the (I'm sure many) bugs in array_pad, but I don't feel that the bugs in array_pad are really relevant to the golfing contest, do you?

And here I thought it might've been a bug in your implementation. If you knew array_pad was flawed, you should've mentioned it. I'm sure I wouldn't have been the first to think that the reference implementation would be correct and could be used to verify results.

MJD says "you can't just make shit up and expect the computer to know what you mean, retardo!"

I run a Win32 PPM repository for perl 5.6.x and 5.8.x -- I take requests (README).

** The third rule of perl club is a statement of fact: pod is sexy.

sub p {
my($a,$z,@x)=@_;
my @n=($z)x(abs @x-abs $a);
@n=abs $a>@x?$a<0?(@n,@x):(@x,@n):@x;
}
[download]

sub p {($a,$b,@x)=@_;@_=($b)x(abs@x-abs$a);@_=abs$a>@x?$a<0?(@_,@x):(@
+x,@_):@x}
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Why can i omit "my" here?

You can't.

Global symbol "@x" requires explicit package name at c:\temp\a_sub.pl 
+line 8.
Global symbol "@x" requires explicit package name at c:\temp\a_sub.pl 
+line 8.
Global symbol "@x" requires explicit package name at c:\temp\a_sub.pl 
+line 8.
Global symbol "@x" requires explicit package name at c:\temp\a_sub.pl 
+line 8.
Global symbol "@x" requires explicit package name at c:\temp\a_sub.pl 
+line 8.
Global symbol "@x" requires explicit package name at c:\temp\a_sub.pl 
+line 8.
Execution of c:\temp\a_sub.pl aborted due to compilation errors.
[download]

---
demerphq

Yes I can.

use strict;
use warnings;

use Test::More tests => 5;

my @x = 1 .. 5;

is_deeply([p( 3, 'x', @x)], [ @x ]);
is_deeply([p(-3, 'x', @x)], [ @x ]);
is_deeply([p( 7, 'x', @x)], [ @x, 'x', 'x' ]);
is_deeply([p(-7, 'x', @x)], [ 'x', 'x', @x ]);

@x = ();
is_deeply([p(-4, 'x', @x)], [ 'x', 'x', 'x', 'x' ]);


sub p {($a,$b,@x)=@_;@_=($b)x(abs@x-abs$a);@_=abs$a>@x?$a<0?(@_,@x):(@
+x,@_):@x}
[download]

Update:
oh dear, @x is a global. silly, me.

holli, regexed monk

55 chars and strict compliant

sub p{($a,$b,@_)=@_;@_<abs$a?p($a,$b,$a<0?($b,@_):(@_,$b)):@_}
    #          1         2         3         4         5
    # 1234567890123456789012345678901234567890123456789012345
[download]