generating a list of identical elements

rovf has asked for the wisdom of the Perl Monks concerning the following question:

I would like to write a function makelist($x,$n), which returns a list of $n elements, each element being the scalar $x. A pretty naive implementation looks like this:

sub makelist {
  my ($elem,$count)=@_;
  my @list;
  $list[$count-1]=0;
  map { $elem } @list
}
[download]

However I wonder if there is a more concise way of doing this, maybe one where I don't need a temporary @list. If it would be a string of $n occurances of $x, I would simply write $x x $n. Can I do something similarily simple for lists?

--
Ronald Fischer <ynnor@mm.st>

Comment on generating a list of identical elements Select or Download Code

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Re: generating a list of identical elements by jethro (Monsignor) on Jan 19, 2011 at 11:33 UTC
You can do this with the x operator as well: `perl -e '$x="ab"; $n= 20; @f= ($x) x $n; print join "\|",@f;' #prints ab\|ab\|ab\|ab\|ab\|ab\|ab\|ab\|ab\|ab\|ab\|ab\|ab\|ab\|ab\|ab\|ab\|ab\|ab\|ab` [download]	[reply] [d/l]
Re^2: generating a list of identical elements by AnomalousMonk (Archbishop) on Jan 19, 2011 at 11:41 UTC
See the `x` operator in the Multiplicative Operators section (fourth paragraph) in perlop.	[reply] [d/l]
Re^2: generating a list of identical elements by rovf (Priest) on Jan 19, 2011 at 11:48 UTC
Great!!! I had not expected this possibility, so I did not look up the definition of this operator. My fault, and thank you for telling me! -- Ronald Fischer <ynnor@mm.st>	[reply] [d/l]
Re^3: generating a list of identical elements by raybies (Chaplain) on Jan 19, 2011 at 13:45 UTC
In Perl, the slogan could be "There's an op for that." ...but someone would probably get sued... --Ray	[reply]
Re: generating a list of identical elements by JavaFan (Canon) on Jan 19, 2011 at 11:41 UTC
If it would be a string of $n occurances of $x, I would simply write $x x $n. Can I do something similarily simple for lists? `@list = ($elem) x $count;` [download]	[reply] [d/l]
Re: generating a list of identical elements by tilly (Archbishop) on Jan 19, 2011 at 16:53 UTC
If you want to use the map version: `sub makelist { my ($elem, $count) = @_; map $elem, 1..$count; }` [download]	[reply] [d/l]
Re: generating a list of identical elements by fisher (Priest) on Jan 19, 2011 at 11:29 UTC
I suppose using push function will be a better solution? I mean, like this: `sub makelist { my @list; for (1..$_[1]) { push @list, $_[0] }; return @list; }` [download]	[reply] [d/l]