http://qs321.pair.com?node_id=11121473


in reply to Manipulating Array Indexes

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11121442
use warnings;

my @data = qw( 1 2 3 4 5 6 7 8 9 8 7 6 5 4 3 2 1 );
my $target = 5;

my @answers = map { $data[$_] == $target ? @data[$_ + 1 .. $_ + 3] : (
+) } 0 .. $#data;
print "@answers\n";

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Outputs: 

6 7 8 4 3 2

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Replies are listed 'Best First'.
Re^2: Manipulating Array Indexes
by GrandFather (Saint) on Sep 08, 2020 at 01:17 UTC

    Try it with: my @data = qw( 5 );.

    Prints:

    Use of uninitialized value $answers[0] in join or string at 11121473.p
+l line 11.
Use of uninitialized value $answers[1] in join or string at 11121473.p
+l line 11.
Use of uninitialized value $answers[2] in join or string at 11121473.p
+l line 11.

    [download]

    Optimising for fewest key strokes only makes sense transmitting to Pluto or beyond
[reply]
[d/l]
[select]

      A) There was no test case for that indicating it is not possible for his data set.
      B) This is one thing I really like about perl - it's easily fixed with just two words and a comma :) 

      #!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11121442
use warnings;

my @data = qw( 5 );
my $target = 5;

my @answers = grep defined, map { $data[$_] == $target ? @data[$_ + 1 
+.. $_ + 3] : () } 0 .. $#data;
print "@answers\n";

      [download]
[reply]
[d/l]

        While I agree with B, I think A is rather a stretch. More importantly, good pedagogy suggests showing how to deal with edge cases is an important element of example code. Golf or obfuscation on the other hand tend to be an impediment to teaching concepts. Slices are important enough to be shown free of clutter.

        Optimising for fewest key strokes only makes sense transmitting to Pluto or beyond
[reply]

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