Re^3: How to get this not the usual round robin looping [updated]


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Re^3: How to get this not the usual round robin looping [updated]

by choroba (Cardinal)

on Oct 13, 2015 at 09:25 UTC ( [id://1144660]=note: print w/replies, xml )

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in reply to Re^2: How to get this not the usual round robin looping
in thread How to get this not the usual round robin looping

You can also complicate it to avoid the loop (in fact, disguise it as a repetition) and the // operator:

push @{ $h{$_} }, shift @B for (@A, reverse @A) x (@B / @A / 2),
                               (@A, reverse @A)[ 0 .. @B % (2 * @A) - 
+1 ];
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Update: Another idea:

for my $i (0 .. $#A) {
    $h{ $A[$i] } = [ @B[ grep { my $m = $_ % (2 * @A);
                                grep $_ == $m, $i, 2 * @A - $i - 1
                              } 0 .. $#B ] ];
}
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TIMTOWTDI, an iterator:

my $iter = do {
    my ($pos, $step) = ('0E0', 1);
    sub {
        my $r = $H{ $A[$pos] } ||= [];
        if ($pos % $#A || $pos =~ /E/) {
            $pos += $step;
        } else {
            $pos .= 'E0';
            $step *= -1;
        }
        return $r
    }
};
push @{ $iter->() }, $_ for @B;
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