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Re: [S29] uniq
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From:
Damian Conway
Date:
May 19, 2005 20:37
Subject:
Re: [S29] uniq
Message ID:
428D5B69.7030908@conway.org
Luke wrote:
>>>I wondered what uniq's default comparator should be, =:=?
>>
>>&infix:<~~>
>
> Woah there. ~~ is a good comparator and all, but it's not the right
> one here. ~~ compares an object and a pattern to see if they match.
> That makes it the right choice for when and grep. But we're trying to
> remove elements that are *the same*, not elements that *match*.
Ah, I missed Larry's message last week where he mused:
> : 3 =:= 3; # always true?
> : 3.id ~~ 3.id; # ditto?
>
> I think immutable values could work that way, especially if we
> want to store only a single representation of each immutable
> string.
If that's now the behaviour of =:= on non-referential values, then I agree
that C<uniq> should compare with the =:= operator.
Of course, that presupposes quite a bit of smarts on the part of the operator.
For example, we'd also need to decide what these evaluate to:
3 =:= 3.0 # ????
3 =:= '3' # ????
They're surely not identical, but you'd probably want C<uniq> to think so.
Or maybe you just have to SWYM and write:
@uniq_nums = uniq +«@nums;
or:
@uniq_strs = uniq ~«@strs;
if you have heterogeneous data.
Damian
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