Damian Conway wrote:
> > Clever, and really obscure;
>
> "Invisible", rather than "obscure", I would say.
> DWIMity of the first order. :-)
>
> > wouldn't this then require that _everyone_ that
> > writes a curried expression for the sort sub use ^a & ^b, and that everyone
> > writing a non-curried sort sub name their parameters a and b?
>
> No, that's the lovely part. If you use positional placeholders or the
> anonymous placeholder, the resulting curried function has *unnamed*
> parameters, so the *order* of the arguments passed by C<sort> is all
> that matters.
So that's what I missed, that you expect named actual parameters to be legally
passable to subs with unnamed formal parameters. I would consider that
inappropriate, needing at least a warning. If people want to use named parameters
with a sub with unnamed formal parameters, they should curry a wrapper.
> So all of these work as expected (as a consequence of the standard
> semantics of named parameters):
>
> @sorted = sort ^b <=> ^a, @list; # reverse sort
> @sorted = sort ^1 <=> ^0, @list; # reverse sort
I note your use of ^0 and ^1 where I and another poster both used ^1 & ^2. I wonder
how many people will have to learn about ^0 if you implement it as a positional
placeholder. Note that regexp produces $1, $2 ..., not $0. And people really do
count from 1, until they've been indoctinated that computer arrays start at 0. But
placeholders are not an array.
> @sorted = sort ^_ <=> ^_, @list; # normal sort
> @sorted = sort {$_[1] <=> $_[0]}, @list; # reverse sort
> @sorted = sort sub{$_[1] <=> $_[0]}, @list; # reverse sort
>
> The only case that traps the unwary is:
>
> @sorted = sort ^y <=> ^x, @list; # normal sort!
>
> But I don't think Larry was worried about that -- just about the inevitable
> resonances with the late unlamented $a and $b.
>
> Damian
--
Glenn
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