On Tue, May 29, 2007 at 02:21:37PM -0400, Mark J. Reed wrote:
: My expectation before reading the delta was that negative counts
: would do a reversal:
: "123" x -1 = "321"
: ('a', 'b', 'c') xx -3 = ('c', 'b', 'a', 'c', 'b', 'a', 'c', 'b', 'a');
: I don't know why I think that makes sense, but it was honestly my
: first thought.  Does it make sense to anyone else?  Is there a
: compelling reason I'm missing for having negative values behave as if
: they were zero rather than adding some other potentially useful
: functionality?

The main rationale for going with null return is that the biggest use of
replication has generally been something like:

    say $foo, ' ' x (20 - $foo.width), $bar

and it would be counterproductive to degrade to "negative" spaces in
such a case.  (This is also the rationale for not returning failure
on negative counts.)

Note, however, that these are just multimethods, so if you defined a
variant that accepted a count of type "Int where *..-1, it would come
earlier in the candidate list than the normal count of type "Int".
So you could give it different semantics if you like.

Arguably, in Perl 6 people might instead write

    say $foo.fmt("%20s"), $bar

but just because people can write it that way doesn't mean they will.
(Plus that approach doesn't work if you want to count tabs.)

And generally, I think

    @list xx -1

is less readable than


so I don't feel inclined to include it as another Way To Do It.


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