Rod Adams <[EMAIL PROTECTED]> writes:
> $re1 = /^ <-[x]>* x <-[x]>* $/; # match a string with exactly one
> 'x' in it.
> $re2 = /^ <-[y]>* y <-[y]>* $/; # ditto 'y'
> $re3 = /^ <-[z]>* z <-[z]>* $/; # ditto 'z'
> $re7 = none($re1, $re2, $re3); # matches if there are 0 or 2+ of
> each of x,y,z.
> #7 I have no idea how to attack as a single RE in anything close to
> approaching elegance.
Depending on your idea of elegance ... anchored zero-width negative
lookahead:
$re7 = qr/^ (?!= $re1 | $re2 | $re3 ) /x;
Oh right. Perl6. Well, if I understand "<$re1>" correctly, I think
this is what it will look like:
$re7 = /^ <!before <$re1> | <$re2> | <$re3> > /;
I still want junctions, but I also still am not quite sure how they
will behave. For instance, I wonder how this would autothread or not:
my sub f (Int $x) {
if $x {
return 0, 1, $x;
}
else {
return 0, 1;
}
}
my $j = 0 | 7;
my @a = (1, f($j), 0);
- How many elements are there in @a? 3? 5? 4|5?
- What is @a[-1]? 0? any(0)? 0|undef?
- What is @a[4]? undef? 0|undef? 0?
Na�vely, I would expect that setting of @a be equivalent to this:
my @a = (1, ([0,1]|[0,1,7]), 0);
And so from the callers perspective, &f, which usually returns two
or three values, suddenly returns a single (junctive) value. New
semantics for &f, courtesy of autothreading. I expect this is too
na�ve. But what am I missing?
Eirik
--
All bridge hands are equally likely, but some are more equally likely
than others.
-- Alan Truscott
